methotrexate injection

Has anyone had the methotrexate injection for miscarriage.

My miscarriage started 3 weeks ago (haven’t bled for a good week) but my HCG levels are still rising.

They are worried it could be tissue left or a missed ectopic so they’ve offered me the injection or to have an operation and remove my tube (which he doesn’t want to do incase it’s not but will if needed)

I’m just worried as he told me loads of side effects and made me sign a disclaimer (which I know they have to do) but I’m now scared.