I agree with PVCpanic that these meds can affect peoplein different ways. I am also a big proponent of medications like Prozac as long as you combine this with talk therapy to gain long term knowledge about this. When i first started on an SSRI, I had a few side effects as well but after a few weeks they mostly subsided as well. I always stress patience when dealing with medication. Just keep in communication with your prescribing doctor to express your concerns and questions...keep us posted!
It can cause weight gain and it can cause weight loss. A lot of people have some fatigue with it so in that case you may be inclined to exercise less etc.. and therefore gain weight. However, over time, fatigue and other side effects usually fade away. How long have you been on it? After 2-3 months side effects are not terribly common. I've been on it for almost 2 months now and I had lots of weird side effects at first (insomnia, nausea, jitteriness, fatigue, and others) but most all of that has faded away and I've found the drugs to be pretty helpful. I certainly have not had any panic attacks. The anxiety has been lessened and/or easier to deal with for me.