Idk if I'm fertile.....

I already have a daughter, she's 7. I had the IUD for a year and a half when I got it removed because it was dislocated. At the same time, my doctor found a small cyst. She told me to go back in 6 weeks and when I went back it was still there, hadn't shrunk or grown. Six years later, I've had 2 relationships where my guy has finished inside me, and we think I'll get pregnant and then nothing. Literally, we'd have sex 3-4 times a night 2-3 times a week and nothing! No birth control. Every time I go to the doctor, I want to talk about it but i get nervous to find out what if I can't have anymore kids!?

My period is super irregular and I've read it could be a few things, that may cause infertility, and it just scares me. My daughter is 7 now and she wants a sibling... I eventually want to give her one. How can I go about talking to my doctor without having a meltdown!?