Feeling very weak and Faint !!!

It sounds like you're dehydrated which can make you feel weak and faint and play with your blood pressure. Your heart is a muscle that needs water to keep the muscle pliant and working well. Up your water if you aren't at 64 ounces a day. Water is really important. You may think it's your lack of calories but you have enough stored fat to get you by for a long time (exactly what my surgeon said). AT 3 weeks out I was getting 100-200 calories per day. I wasn't on shakes. If you  are you're allowed more calories. I wasn't on 800 a day until 8 months out and I was fine, and the norm for my surgeon's post ops. Up your water and see how you're feeling. If you're dehydrated you'll need extra water for a few days to get your levels back up. Force the water, and do the broth and other liquids as needed. Water is way more important now -you can go without food for a while but no****er, and we dehydrate really fast when we're post op. Get in more fluids and see how it is. And my blood pressure was 99/69 for years. It's only gone up a couple numbers in the last few years.

Jen 12 yrs post op RNY

I went through the exact same thing. I felt fine for having major surgery for about 10 days then bam! I was so lethargic. Extremely tired, after showering I wanted to go back to bed before even getting dressed. I pushed through. Upped my protein and started experimenting with different foods. Nothing much but I ate a spoonful of egg salad for example. After about 7-10 days I started feeling normal again. Im almost a month out and all my scars arent completly healed. I take that as a direct sign of how my whole body is doing. Even though we have moments of feeling normal we are still healing.

Get consulted to your gastric bypass surgeon might give you proper medications.