After heart surgery i was on a lot of pain meds. i do not remember much 4 months before and 4 months after surgery, is this because of the meds?

Possibly: Pain meds can impair memory, especially at high doses. But a long surgery with general anesthesia is even more likely. If your heart disease caused delirium or other changes in consciousness, either before or after the surgery, you weren't "there" enough to encode memories. This is called anterograde amnesia, and it's not uncommon in such situations.

Partly : Not just the pain medication but also the general anesthesia affected your memory. Additionally, you may have been having "mini-strokes" or tias due to your heart condition, which could also have affected your memory.