If I only get my period for 3 days and it's very painful and it makes my legs weak and in a lot of pain... What would be the problem? Also Why Do I Have A Hard Time Having Another Baby It's Been 7 years? What could be causing the pain with my period and me not getting pregnant?

I would hope after 7 years you have discussed this with your OB/GYN. It could be hormonal or a medical condition.

There are many medical reasons. And the period may or may not be related to conception issues. Are you properly tracking ovulation with medical testing ? Have both of you been examined to be sure no issues for conception.

But you need to visit your OBGYN and be examined to see why for all of these, we could guess dozens of things, and none may be true, no one will know with out testing