Heaviness at 22 weeks

I’m currently 22 weeks pregnant, in my 3rd pregnancy. Lost 2 other pregnancies at 17 weeks so this time I’m seeing a high risk doctor at NUH who did a cerclage at 18 weeks and advised me to go on bed rest for the remaining weeks of pregnancy. I seem to have a short cervix with some funnelling due to a dynamic cervix. So I was advised not to walk at all and use a wheelchair when I travel to the clinic. (no other travelling outside of the house allowed) The problem is I notice that I feel so heavy whenever I stand up even for a second as if my baby is about to drop out. The doctors have no answer for that except that I do not stand up much. I’m not sure if this is because my muscles have weakened from the lack of movement/ exercise or just that I’m about to pop this baby out anytime. I take progesterone everyday and have a weekly prog injection as well. Does anyone have the same problem or advise for me? Is this a normal pain you get at 22 weeks?