how to calculate fertile period without ovulation kit at home

hello,
       i have pretty much good info about my own health routine,like when my period will be when my ovulation happens etc.but could i be more precise while im trying to get pregnant so as to which time is the best to try getting pregnant?or i should think all the month is good to try?i had sex just 2 days back and yesterday i had a severe cramping pain in both my legs and a sharp pain in my abdomen,was that the ovulation?can i be pregnant?even though i didnt have orgasm during that sex.so is it important to have orgasm to conceive for a female?how long do i need to wait till i take the first response test?