3 years later.. Will it ever happen?

Kylie • Pregnant with a baby girl after 8 years TTC. 💕
3 years ago this past August, I had a miscarriage at 8 weeks. I had just graduated high school and was starting nursing school. Super scared yet, super excited. Completely unplanned. My boyfriend (now fiancé) and I had been together a couple years at this point. 
Anyways, 3 years later... No birth control, no condoms, not trying to prevent in any sort of way.. It still hasn't happened. After my miscarriage, the doc said everything looked fine and it happens.  Well, I feel like it should've happened by now. With 3 faint positives in September,  I believe I had a chemical but, other than that...nothing.
I hate to say it but, I haven't had a full pap since my miscarriage, therefore I haven't asked the doctor to do any further testing. My fiancé and I plan to get married soon so, I'll be on his insurance. We both want to go get checked out and make sure things are fine on both ends but, until then.. It just makes me wonder. 
We've only been "trying" for the past 3 months but, years of unprotected sex regularly, you'd think something would've happened. 
I know there are sooo many people in my same boat. I'm only 22 so, I'm not completely freaking out about it yet but, my fiancé is 25 and we've always wanted kids young. We're both very established and have built our relationship for over 5 years. We're ready to add to the family and fill up all these bedrooms. 
Any advice as to what to do? Have any of you tried preseed or pregprep? I've looked into both. No stores in my area carry it so, I may just have to pay Amazon a visit.