I feel dizzy and body cramps one day after having my first intercourse. what is happening?

First intercourse: not sure. Could be many things. Anxiety about first sex would probably top the list. Be sure you use protection (condoms) and be on birth control to prevent pregnancy. Not uncommon to have some cramps after first intercourse, esp if partner ejaculated into your vagina. Male semen has some properties that can cause some cramps. Be safe.