The best thing someone has ever said is don't stress out, have sex for the fun of it/enjoy, if you get pregnant you do and if you don't just remember next month is a new month.
Another good thing to look into is blood types, maybe it doesn't apply in your case bt if you are RH- and him RH it can cause alot of problems.
Have you tried ovulations tests?? Pap smears coming back normal? Is either one your consumations of alcohol or caffeines increasing (lower sperm count.)
Best bet would be for both of you to see a dr but if you are thinking about fertility treatments I know the drs down here make you wait awhile. I don't know what its like where you are but I would definatly look into things!
The chances that an abortion caused it is rare but it could be a possibility but I know stress can be a huge factor as well!