My girlfriend and I have recently started having vaginal sex three weeks ago and the first two times went great, but suddenly I am having lots of trouble getting or keeping erections. We are very sexually active, and usually have sex when we see each other, which is almost every day. When we started a long time ago, it was only oral or manual, and we were able to go multiple rounds a day. Now we are lucky if I can even go one. I used to jack off multiple times a day too but now it's just really hard to get going and I'm really terrified. This is completely unnatural for me. I don't have any health problems, I don't drink, smoke, or do any drugs. Please help me.