Sorry to hear about the cheater, that's so heartbreaking. What an asshole to put it bluntly.
Most doctors will tell you to wait 12 months given your age. If you have a really nice doctor and asked them to do the simple tests that don't involve invasive measures they might be willing. If you explained you really need the peace of mind? That's a long shot though >.<
Or you could start charting, this will give you an idea if your luteal phase is regular. If you come up with any abnormalities then at least you'd be able to go back to the doctor and show them.
Are you taking any prenatals?
Otherwise it's perfectly normal to be trying this long with no pregnancy yet, so you could hang in there until 12 months and hopefully you'll get pregnant and the worries will all wash away