Dull Left Testicle/groin Pain, Erectile Dysfunction Age 21

Hey guys. Before I start, I want to say thanks for your time and understanding. I hope none of you mind as I try to explain my problem.

I just turned 21 years old and have had sex twice (once recently and a few months back). I discovered masturbating around age 14 by mistake. I used to masturbate about once every two days. I used to "injaculate" (not ejaculate) for the maybe the first few months during age 14, then I realized that ejaculating was the normal thing.

A few years back, I discovered that during ejaculation, my left testicle would "tighten up with feeling" and go up towards the groin, while the right testicle does not (right testicle during ejaculation felt loose and not much feeling). I'm not sure if it was always like that but I assumed it was normal. At that time, I didn't mind.

A few weeks BEFORE I first tried to have sex, I started to get a dull pain near my left lower ab. I don't really know why. I think it's the groin and it feels like the pain is coming from the left testicle. My left testicle does feel more sensitive than my right. If I try to squeeze both testicles, the left testicle would slightly feel more pain. This dull pain usually doesn't even feel like a pain at all. It's more like a stiff feeling that doesn't feel normal and wasn't there before.

Anyways, when attempting to have sex, my penis would get hard, then soft within seconds, hard again, then soft and so on. I can ejaculate but it takes some effort. When my penis won't stay hard, it's embarrassing and not pleasurable. I do not know if the dull pain in my left testicle has something to do with it. I'm attracted to the girl so that's not it.

Now I masturbate maybe every 4-6 days. I was hoping this change may help fight erectile dysfunction and maybe make the dull pain in my left groin go away, but it has not. I've noticed that even during masturbation, my penis gets hard, then soft, hard, and so on. I don't think it's a psychological problem. Any ideas? Any help is appreciated. I'm going to a doctor soon for a general checkup so I'll bring it up with the doc. Some may say use viagra but it's not a common problem for 21 yr old males, so I'll hold off on that. I never tried it but it may not even work in my case. At the moment, I'm avoiding sex. I hope to find out what the problem is first.