If you contracted an std while married but youve been faithful could your partner be lying?

ok , so today my gyno gave me meds for gonorhea and clamidia, all i could do is cry, i have been absolutely faithful to my husband, i told my husband what happened at the dr today, he said he has never cheated, now i am a homemaker hes a truckdriver , he had left me and my children last month, just up and lwft us, hes been back now for 3 weeks, now he first started saying he never cheated and he has no symptoms so hes clean.....#1 im a usual at the gyno, never had this, pluss ive had two kids they test for this ive never had this he said he coulda had it before we were married and gave it to me, is this true that he coulda been faithful and just now gave it to me, well, weve been married 3 years yesturday was our anniversary...what a present lol...