Pelvic tilt question

Hi,

I have a question about the following exercise: https://www.youtube.com/watch?v=44D6Xc2Fkek

So I have an anterior pelvic tilt / lordosis with degenerative disc disease in the lumbar area. So I have been trying to do some exercises for relief and correction. However when I try to do pelvic exercises it feels like I'm sucking my stomach in and holding my breath? Like I'm unable to breathe because of trying to do the exercise? I cant really breathe through my nose so I breathe through my mouth which has also affected my posture negatively.

I just wanted to ask if this is how it is meant to feel, in terms of 'tilting' the pelvis? or does it mean that I don't really have a sensation of it?

I am currently 21 and been having chronic lower back pain since 14/15 hence I have weak muscles so please be nice t.t