Need some advice

Hello I’m 23 been TTC since November 2022 for baby number 2, I got pregnant by accident with our son as I was 17, I don’t get how I can get pregnant by accident at 17 but at 23 I literally can not pregnant I have done absolutely everything, tracking ovulation and always get my peak, folic acid, preseed, just doesn’t help at all for me none of it, my partner did a sperm test and the results come back fine so I know it’s not him, it’s me who’s holding us back for having another baby. I want to book another doctors appointment so they can do more tests for me but last time I explained my situation to the doctors he only booked me in for a blood test 7 days before period is due, what other tests should I have been booked in for? So I can book another appointment and specifically ask for the tests I need, also my blood test come back fine last time, just wanna know what’s wrong with my body, feel like a surrogate would be easier for say this point.