Hey I'm 21 Now And I've Always Had A Problem

Hey I'm 21 now and I've always had a problem w/ my erections. I'm able to get an erection and ejaculate but it still just hangs low and theres no sturdy structure to it. when I was 18 I went to my doctor and went to a specialist where they checked the blood flow and stuff and there was no problems and i didn't pursue it any further. But I want to fix it it just has no structure it doesnt stand up on its own and its never as hard as it should be for my age