My first PB shake.....I don't think it's working

I started taking the PB shakes on Thursday. I started with one before bed with some water. Was up about 5 times urinating but I stuck with it the next day. Friday I did have a BM so I did another PB shake at bedtime. Sat did 2 shakes one before breafast and one at bedtime same on Sunday. The trouble is I feel very constipated, full and bloated. I feel extrememly full after I drink the shake and feel uncomfortable at night with some pain in my back and chest. I have reflux and I'm not sure if the pain is attributed to the stomach being full at night. Saturday I didn't go at all and just had a small BM today and yesterday. Should I up my shakes or give up and try something else. I have been constipated all my life and sometimes go only once a week. Help?????......... Tweet