How long should you let a mental illness grow before seeking professional assistance?
There are many places that will do psychiatric counseling services for little or no cost, and while others span the whole gamut of price ranges, mental health is very important (just as important as physical health.) If you think you may have problems that require the treatment of a licensed physician, do so. Better that you be engaged in prevention than treatment, and better treatment than nothing.
Is autism a mental illness?
The autistic brain quite simply has a notably different neurology in how it functions, much like a cat and dog are different in neurology, though seem mostly alike in many ways: a cat isn't a defective dog, just a cat. Likewise, if a cat attempts to be a dog, it doesn't work so well in practice: a cat that tries to be something it's not (a dog) will end up with mental problems from attempting to live that lie. So, too, will autistics have more psychological problems brought on by trying to (or being forced to externally) act like neurotypical (aka "everyone else") people, because it isn't natural, and results in a lot of long-term stress. Mental illness is something that's transient, or at least it develops over time: autistics are born that way, and it can't be cured, and it doesn't go away with time: it is a developmental difference, and some types of expected developments may not happen, or happen much later, while still other developments may be something neurotypicals never have themselves.
Does doing drugs mess up your mental health?
Yes. Doing drugs can and does mess up your mental health. Marijuana can bring you- Hallucinations, anxiety and panic attacks, increased risk of cancer, long term mental illness,loss of motivation,loss of co-ordination, impaired perception,irreversible lung and respiratory damage.Short term effects of ecstasy are- nausea,hallucinations, sweating, muscle cramps, impaired vision, a raised body temperature which can lead to death In fact the long term effects of ecstasy are still by and large under research by scientists worldwide and it is widely felt that ecstasy causes long term brain damage including depression, memory loss and neuro-psychotic disorders .In fact, any drug has an effect, and messing about with it is dangerous.Even 'just trying it out' is a dangerous action. Well, you can't turn back the clock. I urge you to get help from a reputable mental health practitioner as soon as you possibly can.