Erectile dysfunction help

I lose my erection whenver I'm inside my partner, meaning my penis comes out. It never feels securely in. Generic brand viagra/sildenafil helped a bit like getting me erect before I got in but it still doesn't really work.
I'm 21 years old, not overweight, don't smoke or do drugs etc, only medication i'm on is ritalin. And used to take antidepressants but no longer do.
Have always had this issue with all 3 women I've had sex with.
How do I fix this? If its psychological how is it fixed? I want a quick and easy fix so me and my partner can have enjoyable sex.

I lose my erection whenver I'm inside my partner, meaning my penis comes out. It never feels securely in. Generic brand viagra/sildenafil helped a bit like getting me erect before I got in but it still doesn't really work.
I'm 21 years old, not overweight, don't smoke or do drugs etc, only medication i'm on is ritalin. And used to take antidepressants but no longer do.
Have always had this issue with all 3 women I've had sex with.
How do I fix this? If its psychological how is it fixed? I want a quick and easy fix so me and my partner can have enjoyable sex.

Do you have this issue with other forms of sex or just with intercourse?

Just penetration

That suggests to me that it's a psychological issue not a physical one, which is probably why the sildenafil wasn't much help.
Do you think that the other positions would be better for you?

Maybe. I don't know
iot probably is psychological but what can i do to solve that? as that takes time and my girlfriend might not be willing to wait

Is it that missionary is a massive turn off? Do other forms of sex excite you more? Why won't your gf try other positions?
If it's psychological you should get professional help.

I lose my erection whenver I'm inside my partner, meaning my penis comes out. It never feels securely in. Generic brand viagra/sildenafil helped a bit like getting me erect before I got in but it still doesn't really work.
I'm 21 years old, not overweight, don't smoke or do drugs etc, only medication i'm on is ritalin. And used to take antidepressants but no longer do.
Have always had this issue with all 3 women I've had sex with.
How do I fix this? If its psychological how is it fixed? I want a quick and easy fix so me and my partner can have enjoyable sex.

doggy yes but she said she struggled with it when she did it before.
yes but that takes time, money, and no guaranteed fix. i don't even know where to start. i don't want to lose her and i don't want to put my life on hold

I have. I'm getting tested for testosterone levels and cholesterol and general blood things.
Honestly I'm pretty down about the whole thing right now

I'm not surprised.
(Fwiw I find missionary an appalling position.)

She's on top which is better than me but it just does nothing for me. Every time when I visualise sex its doggy or whatever

This is like reading p*rn

don't read it if you don't like it.

Yesterday she said for the first time she was worried that it was her fault I wasn't maintaining an erection, which I reassured her it absolutely was not. When I asked whether she was more upset about thinking it was her fault, or more upset about her not having good sex, she said the latter. I said if its anxiety based which she thinks it is, it might take time to sort out. She said she didn't want it to take too long, and that she hadn't had long sex in a while.
I was really hurt by this I know she was vocalising what I suspected but I am more upset about this situation than she most likely realises. It's made me question my masculinity and makes me feel weak and its embarassing. I love her but its just upset me that shes thinking of a time limit on this, as if our relationship is dependent on the quality of sex. She has upset me with certain actions/behaviour , but I don't mention them because I try and see the bigger picture and remember why I love her.
I think I would be more devastated not about potentially breaking up, but potentially breaking up because of this issue. I am trying to solve it. I went to the doctors and am having blood tests done.
I honestly don't know how to solve it if its anxiety or psychologically based as I was pretty ****ed up in my late teens with mental health issues and a couple of years on antidepressants. Both my previous sexual encounters resulted in which I failed to maintain an erection to penetrate (though in my girlfriend's case i do have one to actually get in, its just it doesn't stay in), resulted in me being chucked out of the room and blocked.
There are sex positions I want to try but my girlfriend prefers missionary which is fine but I have other ideas. I don't feel our sex is very sexy to begin with, partly because the tablets mean it has to be planned.
I'm hurt and unsure of what to do