My period was heavy the first two days then tapered off to spotting now I gained 4lbs in a week

My AF is usually heavy the first 3 days with lots of clots. She was late and I spotted a day before she came on which never happens. Now she's barely there and I noticed since last week I've gained 4lbs with no changes to my diet I started walking 3 miles a day on Sunday. Maybe that's the weight gain?