Hi
@fhjp and welcome to the forums.
Metformin has been around for a long time (it's also a treatment for PCOS) so the gastric side effects are well known, and though some people tolerate it very well, others really don't.
I must admit I haven't heard of weight loss as a side effect, unless that was a result of the gastric ones (nausea/diarrhoea?).
As a T1 I haven't used it personally though I was on a metformin trial for a couple of years so may or may not have been taking it then (Half the participants were on a placebo).
There are many other diabetic medications and to be honest many of the T2s on here find that reducing the carbs in their diet has a greater effect than metformin.
Can I ask how long you've been diabetic?
Once more, welcome.