Exercise.....i know you want to and then don't, then do, then get annoyed for not....anyway you do not need this you know my opinion and while you don't believe it the truth is the truth wether you believe it or not.
But i think a middle ground is best so here goes:
Exercises you can do in bed....no not those type!!! Get your mind out the gutter...till later...and get your exercise latex on to workout on your bed.
1: Neck roll
releives stress and loosens the muscles and tension around the shoulders and necks. And can be done while sitting down (like on a bed). The benifits are very good.
2: The Pillow Twist??
By the looks of the photo you sit leaning slightly back using your arms under your leg as a guide.....then you magic a pillow into your hands. Once in possession of your magic pillow you twist from side to side you strengthn your back, sides and tummy an alround easy and useful exercise. BUT NOT NEEDED!!
3: Marching Hip Raises
firms up your legs strengthns your back without loosing the bit in between = win win win
4: Toe Touches.
Lets get you ripped abs and firms up your shaply rear
Finally if you are looking at all these and going Rat Bag!! You are pointing out all the bits i don't like and these won't make me fitter!!! You *profanities and insults*. first i don't think you need to to do any of these even once.
as for the getting fitter, you could go out for a run...coming up to winter...bad idea, you could go to the gym but this is your fourth year and you are you so staying close to your work is a must so how about:
30min bouncing work out substitue your bed for the trampoline add in the Hannah greatest hits and i can easily picture you singing and smiling away for over and hour :)
just a thought