TTC @ 39 feeling like all my eggs are just old and dusty.

TTC at 39. Only off BC since July and have had 3 very regular periods. However, first month trying, tested positive on schedule with OPK. Haven't got a positive reading since. Feeling old and disappointed. Have a 20 son and have been on BC since. I know it hasn't been long, just think I may have waited too long.