I'm not sure what "other things" you did before sex. But I've found it helpful to bring masturbationn into the mix while we are together. By showing him what I like, he's able to figure things out better since we are all different. Some guys pick up on things quickly and can handle things on their own...whhile others I've found think that the harder and fast they penetrate you with their fingers- the better it is. Since this is your first sexual relationship, you should feel comfortable enough with him to open up a little. As you get a little older, it won't be so embarrassing to show a guy what you want. They don't need written instructions, but a good praise when they are in the right spot, will help things out on your end. Then talk about it afterward. Sex can be a lot of fun, but don't forget that you need to enjoy it, too. Don't just do it because he likes it. In nmy earlty 20's I made so many mistakes thinking I had to have sex with a guy if I wanted to be with him. I wasn't sleeping around, but I was under a misconception that sex was just a given. THen I met a guy who basically put the brakes on sex and told me that he wanted to be with me and not just the sex. So we waited...eventually we gave in...but I knew him much better by that point and whenever we are together we have amazing sex. Girls are more emotional, so make sure you feel safe and secure with whomever you are with and once you are, you will start to enjoy it. But keep in mind, many women can't orgasm by intercourse- they need clitorus stimulation...so don't stress out over it.
Sex can feel fine or nice without having an orgasm, and some of the ladies who write on this site will tell you it is more usual for a woman not to have one with a man than to have one with a man. I wouldn't be able to prove that from my own experience, but I will tell you that learning to masturbate will definitely mean you can give yourself an orgasm sometimes a lot more easily than you can get one with a guy. LOL
Orgasm has been described as "feeling like your **** is sneezing." This description pretty much covers the spasms that happen as the blood pumps through the vagina. You'll know when you have one, even with a guy, because you generally just want everything to stop for a minute when you're feeling the spasms.
The part about your body not letting you have an orgasm might be that you are getting too self-conscious about performance, and it isn't letting you fully relax. Tell your bf you are not going to focus on orgasm and you don't want him to focus on your orgasm either, in order that you can relax any of that kind of pressure.
Good luck! Be sure! sure! sure! to practice safe sex.
Annie