Clomid and metformin are very different.

Metformin is a drug normally used to treat people with type II diabetes, it helps counter act the insulin resistance that causes PCOS and for some people, metformin alone is enough to make ovulation resume and to allow conception.

Clomid is a drug that is used to "trick" the body into ovulating. I'm afraid I don't know anything about how it may effect a stomach ulcer, or the mood swings, but I can tell you that I'm on an anti-depressent to help deal with anxiety issues, and I had terrible trouble with clomid - there was a lot going on at the time, but I'm sure the clomid didn't help my response one bit! The best way to avoid side effects with clomid is to take it at night before going to bed.

I hope others will be able to give you more information - I've only ever done one clomid cycle, which has failed to work and rather than try it again, we'll be commencing IVF soon.

Good luck!

BW