Periods after miscarriage, is this normal?

[COCKadoodledooo]

I had a mc at just over 11 weeks mid-June. It was described by the consultant as 'pretty nasty' (needed 3 litres of fluids during, more after, plus was taken to theatre for immediate middle of the night erpc when my blood pressure dropped to 80/39).
My first period came about 4 weeks after the initial blood loss stopped. Since then the longest gap between them has been 2.5 weeks, and last night I started my fourth in 6 weeks.
They're heavy, last 5 days to a week, painful and occasionally vomit-inducing. Constipation a few days before, the runs the day they start.
If this is normal following mc, how long until it gets better please?! If not, what can I do about it? I feel hideous. We're away on holiday atm and it's debilitating. I really don't feel up to doing anything today and that's after a nurofen/co-codamol/berocca cocktail!