Sorry there are no physicians on this site. Many of us have a medical background - but sorry - no doctors. That said I'm willing to respond to your question.
First of all size does not have a lot to do with satisfying your spouse. Sex is much more than just the mechanics. The largest sex organ in the human body is the brain! Yes, that is a true statement.
A Urologist may be able to prescribe medications that will help with your erections - but generally not the size. Please don't be fooled by internet sites that promise larger penises - they are a hoax and just want your money.
Before you do anything give you and your partner some time and trial. I assume the two of you have not been intimate or you would already know your partners reaction to your size. Don't worry. Love almost always conquers all. The two of you will be exactly as you said, "Partners." You can work through any issues together.
Your first sexual encounter may not be all you had hoped for - that's normal. The two of you can learn together.
Size never has a thing to do with the ability to reproduce - that lies in your semen - or sperm. If you have sperm and can ejaculate you can reproduce. Relax my friend, sex is an enjoyable experience and add love and patience and the two of you can work this out.
If there are concerns or issues down the road then consult your doctor or Urologist. My friend is married to a man with a penis that is not large - and she reports they have a healthy and happy sex life.
Most men's penis size will be the size of a "cashew" when it is not aroused to ejaculate.
You are worrying unduly about the size of your penis. Because of your worrying about the size of your penis, I am thinking whether this has something to do with you not being able to hold a normal erection. Psychological worries can have an impact on your performance.
Erectile dysfunction can happen to anyone. There are many reasons for erectile dysfunction. If you take some medications, have diabetes or an illness, depression, anxiety, worrying about anything at all, have lack of sleep, under the influence of alcohol - all these things can have an effect on your performance.
First of all, stop worrying about the size of your penis and accept what you have. Once you stop worrying and just enjoy what you do without thinking about the size of your penis, this may be all that is needed.
Your partner loves you for you and not the size of your penis. Like Tuckamore said, the size of the penis has nothing to do whether you can father any children. It is to do with your sperm count.
I suggest you make an appointment to see your doctor and talk to him about your erectile dysfunction so that you can get checked out that all is fine. It may also be a good idea to get your prostate gland checked.
The natural measures to follow to maintain a happy and healthy sex life, is to stay faithful, be yourself, arouse your partner by caressing her and kissing her, make sure that she is well aroused and if her body does not produce enough natural lubrication, use a lubricant like KY jelly before you enter her. Sometimes a woman may be well aroused but her body may still not have produced enough natural lubrication. This can happen any time, but more so as a woman gets older due to hormonal changes.
Have sexual foreplay, you may find that this will help with your erection.
Let her sexually play and arouse you too.
Do make sure you are both clean and always wash your hands after using the toilet. Always wash your hands before touching your partner sexually. After you have sex, don't roll over and ignore her, but give her a cuddle and a kiss. Your wife should go to the toilet to empty her bladder as soon as possible after having sex to avoid getting any urinary tract problems and was as soon as possible. You too should wash your genitals every day.
I have been married for 41 years and my husband always thanks me when we have sex. I have learned to do the same. It is just a little thing like that that makes us feel that we are not taking each other for granted.
To help you have an erection for a longer time, there is a technique that is done, but I am not familiar with it.
If you post your question in the Sexual Health Forum, Dalubaba, is the one to give you good advice.
I wish you and your partner a long an happy life together.