Perimenopause Symptoms: How Do You Know?

How do you know its perimenopause? I am 38, and for the past on and off couple years things have been getting odd with my cycle, moods, etc. It is way worst the past couple months with night sweats I never had them before. Also my period is worst then ever but currently have an iud in. the cramps are so unbearable running down my legs. sex is painful and I am not in the mood like I use to be. I am also eating a lot and feel hungry most the time despite me having had gastric bypass and being great for over 5 years with it.