Meaning it may vary but only by I couple of days. But I'm using this app and I started my period exactly when it said I would
Make sure when you're using the OPK's that you use them around the same time each day and that you don't have anything to drink within 2hours or more before testing. From what you've listed you get your cycle pretty regularly so I don't see why you're not ovulating. As far as having a miscarriage in the past, that shouldn't affect you getting pregnant now. I'm not sure if you got pregnant and miscarried with your current fiance', but with your age you should be fine. If it takes you longer than 1 year to conceive then you and your partner should go see a specialist! Relax and good luck!
what is pretty much? meaning yes your cycles are the same # of days every time or does it vary?
Are your cycles regular? As in, are they the same length every month?
I tried the ovulation tests and I never got a positive
I'm sorry it took so long for you to get a reply. First of all, having a prior miscarriage should not affect your chances of getting pregnant again, so I wouldn't worry about that. As for not being able to conceive right now, keep in mind that it can take a normal, healthy couple up to a year to conceive, so unless you've been trying for a year, I would definitely give it a few more months before worrying about not getting pregnant. The ovulation tests should help! They're a lot more reliable than an ovulation app, since the ovulation day can vary quite a bit from person to person, even with the same length cycles. Best of luck with everything!