Scared to exercise but know I need to

Does anyone else have this conundrum? Where I know exercise would help me sleep better, as it has done in the past, but when the insomnia gets worse (for me it has been due to a very stressful period in my life which has brought on a 4-month-long period of severe insomnia) I feel too tired to exercise. But I also know that sitting indoors all day and doing the bare minimum is just exacerbating my insomnia. But I’m ALSO scared that because my body is already not resting sufficiently, the exercise will have a detrimental effect on my health. I just don’t know what to do!