Sex while pregnant

I’m 8 weeks pregnant, me and my boyfriend had sex earlier tonight and everything was fine, we had sex again about 2 hours later and when I went to wipe myself after he finished I saw brownish blood. I had a sharp pain in my lower left abdomen/ pelvic area and when we switched to doggy it felt weird like a lot of pressure being pushed in so we went back to missionary after. I’m never bled this dark and I’m scared, it’s too late to call my doctor and I can call him tomorrow but in the meantime does anyone know what this means??