Prozac is in the class of SSRI's. Better known as Seratonin Reuptake Inhibitors. It appears that you have been on them for quite some time and these type meds do tend to change within each person's system over time. This can or may alter the desired effects of the intended purpose.

Here is a link with personal comments from other users.

http://www.prozactruth.com/sideeffects.htm

There is also something referred to as Prozac induced anxiety that may be your problem.

However, your comment of "I have always had mood changes" may make one ask if perhaps you may have been misdiagnosed.

The comment of:"I can be happy one minute and be very mad the next" would possibly indicate that perhaps you may be Bipolar Type 1 rapid cycle. (Also known as Manic Depression). These type persons exhibit happiness and care free lives one day and the next may exhibit complete outburst of anger directed to wards anyone or no one in general. Feelings of low self-esteem tend to also go along with Bipolar persons. There are two types. Type 1 and Type 2.

I would strongly suggest mentioning to your primary doctor who is prescribing these to evaluate you for Bipolar Disorder. It can be treated with Lithium and many newer modern medications on the market.

It may also be other issue's that mimic the Bipolar.

It also may just be a matter of your being on Prozac for so long that your body has changed the receptiveness of this medication. Perhaps a change to wellbutrin or other SSRI's would help control your mood swings better then Prozac.

In any event I would most certainly consider discussing this with the current doctor or better yet going to a new doctor to describe your symptoms to see if he may come to the same or different conclusion as your primary.

There are many medications out there to assist you and finding the one that best fits your condition and symptoms is what you need.