Hey I'm 17 and having the same problem.. Are you okay know? I hope there isn't any serious issue..
nevermind...my period came, i just skipped a month almost two...which is weird because i havent skipped in a while, but whatever, it came and thats important...it just hurts like hell now
I think it was around the age of thirteen or fourteen
It's very doubtful you are pregnant unless you've had a penis come in contract with your vagina. At 19 it's likely that your body is still trying to regulate it's hormone production and your menstrual cycle. It's also likely that you have stressed yourself since the "heavy petting" causing your body to skip a cycle or two. Stress, medication, illness, environmental factors and sometimes just a random fluke in the body can cause a missed period or a few missed ones.
At what age did you first start your period?
I highly doubt this. I'm not sure what you mean by petting, but if it's what's in my mind then no, it wouldn't cause pregnancy. I would advise you to see a doctor. Generally they don't want to see you unless you've missed a cycle for 3 months, but all are different. They can give you something to help force your cycle and hopefully be able to determine why you've missed it for so long.