If you think you are pregnant than you should take a home pregnancy test and go to the doctor.
A bit of advice... 16 is a very young age to start a family and 9 times out of 10 couples at that age do not last - not that you won't, but be prepared for anything.... so my advice is, stop trying for 6 months and talk to a trusted adult (doctor, older sibling, etc). 6 months seems like a long time, but it will help you know for sure if this is really what you want.
Also, a very important step in becoming a mother is thinking about the future of your baby and make sure you have considered several things:
1. Do you have health insurance? besides labor (which I've heard can cost upwards of $10,000 with insurance), babies need a lot of medical support to ensure that are no issues early on.
2. Are you in a solid, stable relationship? the last thing you need is to be pregnant or a new mommy and going through a breakup - make sure you have a honest discussion with the father regarding this.
3. Make sure you understand why you want a baby. My sister had a baby because "finally I will have someone who will love me unconditionally"... life has been very difficult for her - she loves her child but because she had selfish motives, she realized after the fact that she wasn't ready
4. Understand how this is going to 100% change your life. Have a plan in place for finishing school and make sure the father does as well.
5. Do you have a good financial source for the baby? They can be expensive... diapers, formula (if needed), doctors, vaccinations, daycare, etc.