Period is late..?

So my son was born December 11 and I had one period so far which was January 25 and it was a normal period and my next period was predicted two days ago.. before I ovulated my husband only pulled out he never came in me but he did like 3-4 days after I ovulated. Well I’m concerned because this baby that I just had I was only 2 months postpartum before I found out I was pregnant with him. So what could be my chance of pregnancy? I took a test a day before my period was late and it was negative but it was also one of those 85cent ones from Walmart.

Also I’m not breastfeeding..