One bowel movement a week, no pain

Hi all

About 5 weeks ago i decided to lose weight as i was overweight, i cut out all my fatty junk that i ugually lived on and started eating healthily - lots of vegetables, some fruit, lean meat etc. Im drinking lots of water.

The weight came off great, in 5 weeks ive lost a stone or so, however- ive gone from a regular bowel movement a day to 1 bowel movement a week!.

I eventually took milk of magnesia this week which gave me diarrhea for 2 days.

I know that my intestines may need time to adjust to a high fibre diet when its been on a low fibre diet- but surely by now it would have adjusted?.

Do i have reason to think something serious is going on? As mentioned i have no abdominal discomfort at all, i just dont feel the urge to go

Thanks.