Asthma inhalers/meds especially albuterol are well known to cause tremor or worsen existing tremors as well as muscle twitching. This is also true for steroids and steroid inhalers. If you need the medications for your asthma, you'll have to work something out with your primary care doc to find the optimal dose of medication without significant adverse effects. Drug use of course is your choice, but I can't imagine the marijuana is helping the asthma. Finally, ecstasy is also well known to cause neurological side effects such as tremor and twitching, especially if it's impure or tainted with unknown agents. If you can, try stopping the drugs for a while and see if your symptoms disappear when you're clean.