Should I take a plan b

So I’m trying not to freak out. Let me start by saying that I am on birth control (Nexplanon) implant but I don’t trust it alone so my boyfriend and I use condoms. Last night we were messing around and I gave him a blow job for like 1 minute before we started having sex. Well we were kissing and everything and I didn’t notice any precum while I was giving him a bj but that doesn’t mean anything. Well anyways at one point I wasn’t wet enough so he spit on his hand and wiped it on me down there so I would get wet. Now I am freaking out that I could have tranferred precum sperm to his mouth and then he transferred it back to vaginal area when he spit. Should I take a plan b? I’m really nervous