No yadnbu!
You could be feeling like this just because you are pregnant, without the added pressure of studying and forthcoming exams.
As you say, you only have two more weeks of this stress, then it will be over. bar the nailbiting whilst waiting for the results
You are putting you, your dh and ds's through this for very good and not totally selfless reasons. You say your dh has been very supportive so far, to give up this close to the finishing line would be more destructive (to your self esteem, potential future, and your relationship) than carrying on.
Grit your teeth, give it your all and anticipate the relief you will feel the night your exams are finished as you kick back and know you have done all you can.
To put a positive spin on your post...you are making a big effort to improve your own and your family's life by doing this studying. You have a lovely supportive dh that you have been married to for 4 years. (congrats btw
)
Ds1 is too young to remember that period of his life where mummy just kept putting cbeebies on for him and had her head stuck in the pc. Ds 2 doesn't really care that you have your head stuck in a pc as long as you eat well, and get rest where you can.
Once your exams are over you will have approx 11 weeks to enjoy the anticipation of ds2's arrival. And once you feel ready to rejoin the workplace you will have a new/better career to look forward to and explore.
It is normal to have these type of dreams in high periods of stress. It just shows how important it is to you, so don't let all the hard work you have done so far go to waste. In 2 weeks time you will be so glad you did it!
Sorry you're not sleeping well, but you must take rest where you can, even if you don't sleep, rest will be of benefit.
FWIW, i have had 2 pregnancies which were during periods of high stress in my life. As i took all 3 of my children to school this morning you wouldn't have been able to tell which one was born of the "ideal" life situation during pregnany!
You are a mummy, therefore you have amazing coping abilities that you probably aren't even aware of yet!
Go on girl, you can do it, only 2 more weeks. That's nothing for all the benefit it will give you in the remaining years of your life.
I'm going to start a cheerleading team....Go alli, go alli, go alli... 
Ps, what profession are you entering?