I've taken both amitriptyline and fluoxetine (Prozac) before. Both on separate occassions.
Many years ago I was prescribed amitriptyline for mile depression and anxiety, but it is also used to treat neuropathic pain so I guess that's why you've had it prescribed for your toothache.
I experienced dizziness and lack of co-ordination with amitriptyline, but not with fluoxetine (Prozac), which I took some years later for a subsequent bout of mild depression. However, I did take them separately, so I can't comment on what they are like to take together.
I'd guess that the side-effects that you are experiencing are much more likely to be related to the amitriptyline, which acts on the central nervous system. It's known to have more serious side-effects, which is why SSRIs (such as Prozac) tend to be preferred for depression these days - there's better compliance with them.
The only side-effect I sufered from whilst on Prozac was nightmares. I was switched onto Citalopram BUT I would say that overall the side effects I had whilst taking amitriptyline were significantly worse than with the fluoxetine. IF I remember rightly, dizziness can be a side effect of fluoxetine also, although in my case I only suffered from this when on amitriptyline.
I didn't gain weight on either drug. I thought Prozac was more likely to be associated with weight loss than weight gain. I think it's been linked with nausea, vomiting and loss of appetite.
What do the leaflets, which was supplied with each medicine, say with respect to side effects?
If you are concerned, I'd say speak to your GP or pharmacist. Also, as you've been prescribed antidepressants, I assume your GP has you booked in for a review appointment in a couple of weeks or so? If this is the case, definitely mention it. They can lower drug doses to lessen side effects.