I'm in a similar situation. My DD is 22 months and we've been trying 5 months for #2. With her it worked on the second try.
The Dr's say since you've conceived successfully you should be able to do it again, so I would assume that would be the case for you as long as nothing has dramatically changed in anyone's fitness or hormone levels.
I've been charting for three months and did a OPK twice, so it looks like I was predicting my ovulation too early. It might not hurt to try an OPK.
DH just got his sperm checked and the results seem like everything is in the normal to low normal area, so we are very hopefull. (He's been on Testosterone Replacement Treatment for a year, which can lower your sperm count.) But we still need to talk to the Dr for the full explanaition and see if he needs to alter his TRT.
I would suggest to just stick with it, and hopefully everything will come together. Although, since you are getting anxious (as I'm sure most all of us here are!) you could try the OPK, BBT charting, or even try the at home fertillity kits. I've seen ones for women and men. They're proably not as accurate as going to the Dr, but could be an option.
Best of luck and keep positive!