I took 4 hpt came positive . but had brown spotting again 2 weeks later than the first time which was i guess implantation bleeding. what does it mean?

Can't say for sure: Congratulations on your + test. The bleeding 2 weeks later is not implantation bleeding. Please test again, and see a doctor.

Pregnancy bleeding: It is very important to be seen by your obgyn. Based on your timing you would be 6 weeks pregnant with bleeding. That can be normal, it can be a sign of a possible miscarriage, or it can be a sign of an ectopic pregnancy. Also, you need to make sure your blood type is not rh - since you might also need treatment for that.