Could i be pregnant?

i've had 3 period since the last time i have sex bt i feel pregnant i go and get weird cramps that ive never have before and also mild headache that ive never had formerly other than that theres no physical change and my periods are conventional i took a test right after what i believed to be implantation bleeding and it come out neg, but it coulda been my length not sure what do you think It could be stress or a short time ago part of your time of year that you haven't noticed until immediately because you are worried. Seeing as you had your interval three times, you are almost positively not pregnant, but it is possible for a woman to get a spell like bleeding during pregnancy. This tend t happen to women who hold had children up to that time, so I don't think you enjoy anything to worry nearly!
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go see a dr - could be std