I'm scared of an unwanted pregnancy, advice?

I am very concerned about a potential pregnancy. At the beginning of this month, I had genital contact with a guy but absolutely no penetration or ejaculation. However, I've calculated that I was ovulating at that time and I'm worried about pre-*** being a factor. My period was about a month and 5 days ago and I typically am on a 28-35 day cycle so I'm not completely late but I'm getting more scared as each day passes. I've also been feeling some symptoms: back aches and frequent urination/constipation. My only optimistic thought is that they could be caused by the overwhelming anxiety I feel. I'm so scared and want to know if I have a good chance of being pregnant and whether it would be too early to take a pregnancy test (it's been 20 days since the genital contact)