Re: Focalin makes me sleepy and tired..
I don't have time to answer you properly, so don't take my brevity for apathy.
Short answer, while it's considered a paradoxical effect, yes, stimulants can make you drowsy. More often though, it's more to do with insufficient sleep than odd med effects. It doesn't make sense, but sometimes the stimulant wakes your brain up to the fact that it needs sleep. I would consider your sleep patterns first, if that's not the answer, a change in medication is warranted.
Yes, many drugs, including stimulants can suppress your immune system to some degree. On the other hand, it may again be lack of sleep, especially since stimulants can disrupt your sleep patterns.