Hi There!
It generally doesn't take too long to feel the effects of the medication - a couple of weeks I would say max. But as long as it isn't too high of a dose for you it isn't going to be an earth shattering difference you will feel. It is something you will look back at after a while and go "wow, usually I would have crashed by this time of the day but I feel fine."
Hypothyroidism makes it a little more difficult to lose weight but not impossible. You just have to work a little harder than the average person. But you ask if anyone had experiences with weight gain so maybe you haven't had that issue yet. If that is true, you may not have an issue since you are now on medication.
I hope this helps and makes sense!
