It drives me crazy that so many people are so shy when it comes to talking about their sexual parts. What is so wrong with talking about a penis or a vagina? My husband wouldn't even call it a penis and a vagina until I tripped out on him one day about wanting to teach our daughters the right things so they aren't shy, scared, nervous, or embarrassed to talk to use about things they need help with (especially if or when they decide to become sexually active).
It's not the size that counts honey, it's what you do with it. Trust me, as a woman I can tell you I've been with guys in my past with huge (12'') penis's that couldn't get me off if their lives depended on it and I've been with guys with what I guess would be average sized (5''-7'') that could get me off no problem and give me multiples. No don't get me wrong, I'm no little hussy and I haven't been with a ton of guys, but this is what I've experienced. You need to know how to work it and how to listen. If a woman can gt passed her shyness with you she will tell you what she wants, what you do wrong, and what you do right...you just have to let her know she can and stick by it.
Issues staying erect in something you need to discuss with your doctor. I don't have a penis so I don't know what doctor, but these guys seem to all be tellin' you the same thing so I'd take their advice.
You say you cum fast too. Well it may be just a per-ejaculation issue or it may be your own insecurities. Either way you can get help for it. No doctor, male or female, will be unprofessional regarding these types of concerns. Don't be shy, just take care of yourself ok and smile, nothing is sexier than a nice smile.