If you have absolutely no side effects/ change from your first week of an ssri, does this mean it may be ineffective for you even after a few months?

No.: If you have no side effects in the first week, then it just means you are able to tolerate the medication. You may have a good response to the medicine without experiencing any side effects.

No : While side effects generally are experienced within twenty four to forty eight hours, it may be that you are simply on a very low dose of your medication, and it is showing no side effects or benefits. Also, most ssri's have very few side effects, and the benefits tend not to become apparent for a few weeks, and take a month or two to fully max out. Talk to your treating physician about this.

No, it doesn't: Whether or not you have side effects, ssri's still require at least 4-6 weeks' consistent dosing for beneficial effect. In many cases, side effects may show up before then. If you're not having any in the first week, simply be glad and keep on with the program. See what results you might get. Best wishes.