Hello.
Everyone wants an iron-clad guarantee regarding whether they could be pregnant. I urge you to learn more about pregnancy and birth control. In the meantime, if your boyfriend ejaculated and if his sperm have reached your vagina, there's always a possibility of pregnancy. I can't tell from your description whether this is the case. In order to find out for sure, buy a home pregnancy kit. Dr. J
I don't know how old you are but.......NO!
First he had his pants on, it was you naked leaving your wet spot on his pants. Did he ejaculate? (***) I dont think you have anything to worry about. And if you couldn't answer this yourself, perhaps you don't need to be dry humping, or having sex.