Just started ttc...

I have been trying for two months and to be honest I know I could be at the start of a long journey!!! Any advice would be gratefully received. I have bought some ovulation tests and taken them however they did not come back positive when I calculated when I was due to ovulate. Is this normal? My periods are always every 28 days without fail so I would have thought that predictions for ovulation would be fairly accurate? I am 36 with no known problems with fertility however I am concerned about my age.