PLEASE HELP ME !!!

I really don't know what to do because I had sex for the first time two nights ago, and i am on the pill so we had unprotected sex (he said he had been tested for std's and is fine but I realise now it was kinda stupid to not use a condom as well). But anyway I can't change that now and on the night I had sex I took my pill about 4 hours late. I'm freaking myself out that I could be pregnant! I don't know whether to go buy and take a morning after pill just in case?? I heard it's quite harsh on the body and shouldn't be taken if you don't really need it. So I can't decide whether I actually need it or not - does taking the pill 4 hours late mean I could be pregnant? It was also the 6th day of a new pack (so within the first week). Someone please help me I'm honestly desperate!! But I'm not sure if I'm just paranoid for no reason.