i had sexual intercourse twice around early/mid march

on march the 30th i recieved the depo injection which was told it will last 2/3 months

now being late september i still have had no period since my breast have largely grown and have stretch marks my stomach looks like it is bloated all the time but i have never had a flat stomach besides that i have only felt sick a couple times and put on about 2 to 3 kgs roughly but that might be just because i sometimes eat the wrong food 

i am so unsure , im only 17 about to be 18 and worried