Am I pregnant? If not then what happened to my body?

Patient: Hi Dr.,Me and my bf had sex without using condom for only few seconds, will i might be pregnant after that? But i after that day, in the next 2 days i got my period as normally. But when i finished my period, i keep feel a lot of strange symptoms likes pregnant. So i bought the pregnancy kit test and tested it at home and it showed negative but i’m still feel unsure about that. Everyday my heart feel so pressure and short breath and also pain + i always feel dizzy and headache, my lower back is so pain like when i having period, my body also feel so tired and keep want to go sleep. Sometimes, i also will feel like vomit when i’m eating. I already felt like that for more than 1 week. And recently, my stomach feel so pain and it cramps around from the most upper part to 2 sides and the lower part of my stomach so i really don’t know what happen to me. Please advises!

Symptoms: Body tired
headache + dizzy
back pain