If going to a Doctor requires parental consent, then I guess where you live you are under-age
Based on what you have stated, I would say that your periods want to come, but wont. It is common for that to happen alot plays in to the factor.. Stress and I gather you are stressing about this.
You used precaution, you have tried a pregnancy test which is negative.. I suggest you stop stressing.
Our bodies are amazing, it can go out of wack just like that.