Teaching is tiring and frustrating enough when not dealing with pregnancy as well! On the plus side, you have a half-term break coming up and the pressure seems to ease in the last half-term of the school year (in Secondary at least) as things wind down for the summer. If you are really at your wit's end with stress and exhaustion, you need to see your GP and consider being signed off. Are you on a contract, in which case you'd continue to be paid? If on Daily paid supply rate you might get Incapacity Benefit.