As a UK doctor I really wanted to give you a UK doctor's perspective and advise you to be very careful with the xanax.
Xanax is not available in the UK, it cannot be prescribed on the NHS and is only prescribed under very strict circumstances by a few specialists. (Usually people who arrive on it from another country are the ones who will have it prescribed but even then they are changed to a different one, usually diazepam.) Therefore I am concerned that you might be buying this elsewhere and may actually be receiving a fake or contaminated drug. Even if it is not fake, xanax is much more addictive than the other diazepams and can be very hard to come off. That's why it is not used in the UK (it's not a cost thing....60 tablets on the NHS used to be only £2 to £5).
It is widely used in the US so you will get different opinions from US and UK doctors.
Please go and talk this through with your GP and also ask for a referral to see a specialist about this anxiety. You are very young still and there are other drugs available to help treat this anxiety.
In the meantime most UK GPs will consider short courses of diazepam (a 5mg dose of diazepam=0.5mg xanax) and you would have the peace of mind of knowing the drugs are official and not at risk of contamination. I have certainly prescribed diazepam from time to time.
Also with regards to the marajuana there is a lot of evidence emerging that whilst it may not cause anxiety in an otherwise calm person it can make pre-existing anxiety worse.
Please see this website (which is American)
Please just stay safe OK?
All the best.
I am a caring and compassionate UK doctor and have been qualified for 23 years. I have widespread experience in GP and cancer care.