erection comes and goes

weather i am jo or having sex my cock gets harder and softer some times to the point that i cant continue with sex for a bit. other times it gets super hard but wnt stay hard for longer than 20 seconds with out stimulation. any thoughts? i'd appreciate any input

There are so many factors that could be involved, so I'll just mention one with which I have personal experience.

Cardio fitness helps me to keep it harder longer. A few years ago, I raised the bar with running and cycling. My return to a higher level of fitness made my erections harder, last longer, and now it's very rare that I go limp during sex. 5 years ago, I'd only get off half of the times that I had sex, and it was a struggle. Now I bust a nut every time, and it's usually very intense - just like when I was 25.

If you don't get regular hard cardio workouts, get involved with some heart pumping recreation. Jogging/running is the best thing for getting a lot of intensity in a short amount of time. Cycling, rollerblading, or brisk walking will do it, too.

check out my response to a similar problem . here is the link:
"Bigger" may not be "better"

are you like, under any new kinds of stress?

Yeah stress a big factor. But it could be so many things. Maybe your partner isn't doing it for you and either you need to spice it up or change up? You could actually have low testosterone. There are so many reasons that this could happen and each person is different.

By the way, what is a healthy refractory period? I've heard that prolonged erections (like, over two hours) can be unhealthy, so I was just wondering. I'll seriously be able to stay hard after having even up to three orgasms, and I was just wondering if that might be indicative of something bad...

I'd say that is indicative of something very good. Also I'd say that puts you into a very small minority of lucky men.

erection comes and goes ...

... well, how like an erection.