Contraceptive Help & Advice Please :)

Ive recently become sexually active, myself and the guy I'm seeing haven’t worn any protection during intercourse. I am only 19 years old, however, I don't want to hope and pray that I don't fall pregnant by accident :/

I'm looking for advice on a kind of contraceptive that won't affect the length, flow, or mess up my periods because they are consistent and rarely ever late or anything that will effect my weight.

Please help me girls :)