Hello.
There are several things going on here.
1. Your break-up: Has it occurred to you that you might have begun being sexual with women before you had resolved all your feelings about your ex? This is quite understandable. It takes time to move on. You may have thought you were over your ex, but perhaps she's still with you; hence, your inhibition. You might want to look at this and make your peace with it so you can begin the rest of your life. Even if you felt the slightest twinge the first time you had sex after the break-up, this could contribute to your beginning to feel anxious and uncomfortable, which then becomes a self-fulfilling prophesy: the more you worry, the more your penis doesn't cooperate. Something about being sexual with others is causing you anxiety. What do you suppose it is? Is it possible that you’re worrying yourself into this problem? In other words, once you began to worry, you stopped being able to enjoy yourself, so naturally, your erections disappeared. Often, anxiety and nervousness create a situation in which you can't relax enough to feel pleasure.
2. Penis size: Iisn't it time to stop worrying about something you have no control over? Sounds like you’ve bought into the myth that you have to have a larger-than-life penis in order to have great sex. In fact, nothing could be further from the truth.
Our society does a terrible disservice to men by raising them to think that their penis has to be 10 inches long, hard as a rock and last all night. It’s no wonder that many men feel insecure about their penis. Locker room etiquette dictates no staring, so most straight men have only glimpsed other penis sizes and shapes in commercial sex videos, which generally feature men with large penises. If you think everyone else looks like a male porn star, of course you’re going to feel inadequate!
Another contributing factor to this attitude is that while most men see their penises several times a day during urination, they’re usually staring down at their penis, creating a visual distortion that actually makes it appear smaller than it really is.
Like noses, penises all have the same basic shape, with some variation. Let’s consider a few basic facts. For instance, did you know that you can’t tell the size of a man’s erect penis based simply on what it looks like when flaccid (un-erect)? Most penises erect to between 4 and 6 inches, and there’s not much variation in erection size (with exceptions, of course). However, when flaccid, there is much more variation. Some men’s penises are 1 inch when flaccid (we’ll call these growers), and others are 5 inches (we’ll call these show-ers). BUT: during erection, the 1-inch penis may grow to the same 6-inch erect size as the 5-incher. That’s right; despite their differences when flaccid, they’ll both erect to approximately the same size. Why don’t most of us realize this? Because most of us just don’t get the opportunity to see men when they’re flaccid and then erect. And did I mention shrinkage? When men are cold or nervous, the penis and testicles pull up into the body for protection (“I’m hiding!”). If you see a penis right after it’s been in a cold swimming pool, I guarantee it will not resemble its erect self in any way!
There are no magic pills, etc., than can change your penis size. Here’s a thought: why not relax, value your penis for the size and shape it is, and be thoughtful about its care and handling. If you do, it will serve you well your whole life.
3. It also sounds as though you believe that self-pleasuring is somehow harmful or can be done “too much” or that you've become desensitized. The truth is that everyone has different needs and different sexual interests. Some people self-pleasure five times a day, some never, some 5 times a week, some once a month, some 10 times a day, etc. You get the picture, right? Whatever works for you is what works for you.
However, building up erotic tension can be fun. If you are anticipating being sexual with someone, try not having an orgasm for a day or two and see what happens. Perhaps a little erotic tension might just be the spark you need. Or just play with building up erotic tension before self-pleasuring and see what happens.
Welcome to your 20’s! When you're younger and just beginning to be sexual with others, erections pop up everywhere--including when you don't want them! Post-pubescent men are highly excitable. After all, sex with a partner is new, and anything new is terribly exciting. As you age, you'll find that erections sometimes take longer, and even come and go. This is not an indication if ill health, but just part of life.
Since you experience erections during self-pleasuring, it’s probable that there’s no medical or physiological condition interfering—it’s all in your head. However, to be sure you have no underlying physiological cause, you might want to see a urologist for some tests.
Worrying about erections is a dead-end street. All it will do is make you anxious, which will make your penis very uncooperative. And remember you don't need an erection to be sexual, have fun, experience pleasure, etc. Relax, enjoy your own unique sexuality and stop judging yourself.
For more information about male sexual issues, I recommend “The New Male Sexuality,” by Bernie Zilbergeld, Ph.D., widely available online, both used and in paperback. Best of luck to you. Dr. J