Scared. Please read.

So I've had sex a couple weeks ago and my period is never regular. There is honestly no way I could be pregnant given that there was no Precum or anything touching me without a condom. He had one on the whole time. And he didn't finish until maybe 5 minutes later and it wasn't inside me when he did. I took four pregnancy tests. The clear blue kind and two were 4 to 5 days after we had sex and they were both negative and I took two a week and a couple days after exactly a month since my previous period. They were both negative. And now it's going one a week after the last two tests and I still have no period.  I'm thinking it could be because I'm never on time but I would just really like some advice.