Here is a link to DMSA if you wish to try it, you can order it from here:
http://www.vivagen.net/detoxprods.htm?If you scroll down the page a bit, you will see the bottle of DMSA. It's the second one from the top, containing 120 capsules and they are 25 mg ones. This is a good dose to start, becuase it's not too high. Though some people have to start even lower, so they split the capsule in half if that is the case. And take about 12.5 mg instead. But 25 is a pretty good dose.
If you do get them and wish to try them, I would recommend to take them according to Andy Cutler's method (every 4 hour dosage). many people are doing this and finding relief. Some do not tolerate DMSA, so they may need to give it a miss. But to my mind it is well worth a try, as it will start reducing your blood levels of mercury and may provide relief, at last over time.
It is hard to predict how long it will take for you to improve. If the DMSA suits you? you may find yourself improving over time. Some find it can help them immediately, some have to wait a while. Usually it can take months to reduce enough mercury to where people start seeing more results, but again DMSA can sometimes provide immediate relief because it can also help suppress symptoms if it's taken every 4 hours because it acts to keep mercury more stable, as it's removing it at the sametime.
It depends on the person. Some find it may increase some symptoms instead, as it's moving mercury. So you never know which way it'll go. Symptom increase isn't a bad thing, so long as it's not beyond tolerance. Mercury being moved is not always possible not to notice it because mercury is so toxic, therefore moving it in anyway will usually aggravate symptoms. It also depends on how poisoned you are, so side effects are not always avoidable.