Help Me

Ok so me and my boyfriend we have had sex... But i havent has my period in 2 months.... We use protection but i feel like im getting fatter and i kinda eat alot..... I am 15 years old and is in 10th grade.... Im really scared because i dont know if its nothin or something. My brother was in a bad wreak and i went through alit of stress for 3 months and had my period 4 times in one mouth..... I dont know what is happening...... Help ! đŸ˜­