Although I never imagined having sex until I was married I still agreed

I'm a 16-year-old Muslim girl. Me and my boyfriend have been together for nearly 2 years and I truly love him.

Just a couple of months back I was at his house and he wanted to have sex although I've never imagined having sex until I was married I still agreed.

I missed my period the first month after I was active. I took a pregnancy test and it was negative but then I had my period a couple of days later so I was late only by a few days.

Then we had sex again and I got my period late again the next month. I took another pregnancy test and it was negative again. 

The thing is I don't know why I get my periods late. Sometimes I ask myself probably it's because I'm sexually active? But we've only used a condom once and that was the first time so I'm not sure.

In the past 2 months we've had sex about 7 times and now I'm still waiting for my period but this time I'm now 2 weeks late. I'm so scared I can never tell my parents about this.

Sometimes I feel like just taking a few of my dad's depression tablets and just leaving this world to get away from problems as I've got so many other problems on top of that.

I've started smoking to help get me out of this world for a bit so I don't have to think about my problems, but it comes back after an hour or so.

I don't know what to do. I need serious help  I just keep having negative thoughts. I need someone to talk to that has been through the same so we can relate :'( (I wish I could tell you more, but I don't know where to start from).