Feeling sad/Ovulation/Irregular Cycle

LC

I have crazy irregular cycles since going off my BC. My doctor said my hormone levels were in normal range. I got a positive OPK late in my cycle day 25. My sister (who has been TTC for 5+ years) said people who don't have regular cycles won't ovulate or get pregnant that way.

I guess I now feel sad and lost a little faith. I had sex the night before I got my positive OPK and the night of. So I was feeling hopeful that this was the month.

Any extra information or advice would be great.