Unfortunately, even with standard use, with all precautions, there is a failure rate of 15 percent with condom use. Since you have history of delayed periods or better to say, 37-day cycles, please wait for your natural period to occur and go for a HPT with a fresh early morning sample of urine 3-7 days later if you do not see your period. If you wish for an earlier and better confirmation, please get an estimation of the serum beta-hCG
titres. This test is more sensitive and specific. Hope this helps.