Metformin and Stomach (not bowel) issues?

I've been on regular-release metformin since November last year and although I did have a few bowel troubles with them to begin with, everything settled down quite quickly and I have been taking them without problems every since. However, for the Iast six weeks are so I have been suffering some stomach (not bowel, very definitely stomach) aches which don't seem related to what I eat or drink. The aches are not constant (one day on, one or a few days off, that sort of pattern) The pain is not shooting,just a general ache, nor is it very strong (say 2 out of 10) but it is beginning to get me down. I have seen a doc and was prescribed some antacids which did appear to help but it could have been co-incidental (it does come and go). I also had a stool test for H-pylori and occult blood in stool and it came back clear.

I am planning on going back to the docs but I was wondering if it could be the metformin irritating my stomach lining? Has anyone else developed problems with met after being fine on them for a while, particularly stomach problems? I'd not be keen to come off the metformin as it seems to be working well for me but really I would just like the aches to stop!

Any help appreciated

Thank you both for your very quick responses. Diet is pretty much the same as it has been since DX, Last hba1c was 5.8 in old money, no anti-or pro- biotics in diet.

I realise this might be nothing to do with the metformin, that's why I was asking for any experiences.