The first 1-2 days of my cycle, it feels like my uterus is falling out since having a c-section. it's very painful, moreso when i am standing, should i be concerned?

Exam may be in order: After any surgery, the visible incision may heal within a few days, but the inside tissues and organs take longer to completely heal. When having a period, your uterus contracts, making the surrounding structures, even more sore. As time passes, and organs and tissues involved heal, your periods should become less painful. I would recommend you go back to your OBGYN for evaluation.