Age: 18, Gender: Male

I am getting a numbness feeling in my body parts such as hands and legs. Whenever I sit there is a weird crawling sensation in my back particularly near the spine and it travels up and down my back. Basically I have to sit for 5 to 6 hours a day for study related work, and more for non-study related tasks, as I use the bed only at night for sleeping and I don't lie down the whole day. I also have to use the computer and also need to handwrite for long hours. The symptoms come and go but they are progressing with time. I am worried if this is something serious. I have been taking vitamins (B12) and supplements for calcium but it is not helping. The symptoms mainly show when I am sitting either on the chair or on the bed, but now they even show when I am standing erect, and it is mainly a pressure in my spine. There seems to be some improvement when I try to keep my back straight but as soon as I bend my back the weird tingling sensation and crawling sensations start happening in my spine. It's not that I lack physical activity because I walk a lot, and I wonder if walking is helping me or worsening the condition. Also doing some exercise like stretches help me and the symptoms practically go away on doing them. Also I would like to add that whenever I get up after sleeping or after taking a nap, one of my limbs are often numb and this is happening for a month now, although symptoms have started to get really serious for the past 2-4 days. Also I would like to add that I have gastro intestinal related problems as well including acid reflux and dysphagia, from the past month. I would be really greateful to you for letting me know what I should do further and what is this because of.

History of medical conditions:
The tingling sensation has been serious for the past week and the numbness in my limbs particularly after waking up has started from the past month which I assumed to be because of incorrect sleeping posture.
Current medication details:
Supplements like Mecobalamine (Neurokind, Vit B12) and Shelcal (Calcium)
Height, Weight:-
5' 8" (172.72 cm), 167 lbs (75.75 kg)