Anak, please go to a doctor or clinic as soon as you can para ma-check properly, they can do a pregnancy test and make sure everything is okay. I know it's scary, lalo na first time mo, pero irregular period ka talaga kaya mahirap mag-assume lang. A few of us moms here had similar situations and ang best thing na nagawa namin is get checked right away para ma-ease ang worries. The pintig and firmness you're feeling, deserve mo na ma-explain ng doctor para you'll know exactly what's happening. Wag mag-overthink pa, okay? Go get tested na, and you'll have real answers. Praying for you, girl.