What Causes Leg Cramping With Tingling And Joints Pain?

I think my potassium level is on the low side. I've had gastric bypass 2 yrs ago. I take b-12,mult vit,as well as many others. in the last few months my legs cramp. I can't walk for more then 20 mins or so. my joints hurt. my legs will tingle. I'm having a very hard time eating uncooked veg. and fruits. I've just started eating veg and fruit in baby food as well as dry cereral in oat brand. how long does it take for me to start feeling better. or have I already done damage to things. I know I need to see my Dr for blood work. but wanted to know how long it takes to get your system. I've just started today eating about 2000 mg per day. do I need more?