bleeding

Alexandria • Ds born 24/12/12 miscarriage 05/04/17 ectopic 04/10/17 DD born 03/11/19
I'm 6 weeks 3 days today this is my 2nd pregnancy I already have a lovey little boy who is 4 years old. I was just at my friends little girls 3rd birthday party and I could feel something leaking out, so I went to the toilet and it was blood, it was quite discoloured brown tinge to it. 
I'm just panicking as I did not bleed in my first pregnancy at all. Keep having a mild twinge cramp like as well and just worrying the worst possible outcome, has anyone else experienced this in pregnancy before and what happened. 
Forgot to mention as it is a birthday party the birthday girl wanted me to jump on the bouncy castle with her so I did for literally 2 minutes and then I was as exhausted so got off could this of caused some old blood to fall down maybe?