I dont know who my baby daddy is.?

I am married to a man I detest(call it due to family pressure). I regret it every day of my life, but what can I do, I can't leave him(though that's what I want the most). U see, I come from a very traditional home. The marriage has turned me into what I detest the most, a cheating wife, but dats d only time I eva have any semblance of happiness and I actually feel alive. Now, I'm pregnant and I'm not sure who my baby daddy is. You see, I saw my period on the 14th or 15th of Nov. Slept with my hubby on the 26th of Nov, but equally had unprotected sex wit my lover on the 1st of dec. 2 wks later, I started having pregnancy symptoms. Had 2 home tests and 1 at the hospital, all negative. On the 22nd of dec(11 days late), I saw my period, but it was not the usual flow. But I figured I was not pregnant anymore and went on with business as usual. Since then I've not seen my period and when I was ovulating(assumed I ovulated btw the 1st of jan and d 6th of the same month), I slept with no one. I slept with my boyfriend on the 17 of january. I've done 2 pregnancy tests and a scan and I'm pregnant. The scan only showed a gestational sac(that's the first stage). Please can anybody help me. Could I have been pregnant all along, since december. please I need to know, not cos I care what my husband will do, but cause of the shame I will face. If I conceived in dec, I will be ok with it, but if I conceived in january, then I can't keep the baby, cos it will be so obvious that the baby is not his. I hope to leave my husband one day, but I need to be stronger first(to face whateva issues might arise with my family wen I divorce him).