I'm really concerned because I've been married for a couple of weeks now and I'm having trouble with intercourse. My erection just doesn't stay firm when I try to enter my partner. It'll start off fine, but then I lose it right at that moment. If I manage to get it up again, the same thing happens. I'm starting to feel really down about this and I'm worried if it's a permanent issue. Also, I'm worried my penis might not be big enough for sex, it's about 11 centimeters. Is this something that can be fixed?