pain in legs

when weather changes to hot i feel very mild pain in my legs only in the area below knees.i think it is because of my bad digestion or sometimes i feel constipation...in the time of pain i do not pass stool normally it is like squeezed.....for the last 6 years i had rash in my anus...my be piles..now it is not so....my belly is somewhat enlarged and have gases...my age is 38 years and i m male and married for the last 5 years
please advise me
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