I'm really scared

I had an ectopic pregnancy with methotrexate shot 2/4. Everything went fine got the okay to be intimate again with protection... My husband and I had a condom break about a week and a half ago, we took plan B right then just in case. Now I've been feeling nauseous for 2 days and like I'm pregnant. Well I got a super faint positive mid day urine, I'm going to retest tomorrow and probably the next day. I'm terrified right now. Has this happened to anyone with everything ending up being okay??? Or maybe it's just a fluke test?? We've done everything to protect against it, I really want to cry. I asked about other birth control but he didn't want to give me anything because he didn't want to increase chance of twins when I get off of it.