I am a bit worried as i am unsure if my employer will extend LMIA and I am pregnant and dont know what will happen if my work permit expires.
You can also switch to a new / different employer if you can find a different employer willing to give you a job offer and get an approved LMIA. You can then apply for a new closed work permit.
If nothing ends up working out and you are at the point where your work permit is expiring, then you would need to change your status to visitor to be able to remain in Canada. However with visitor status you obviously cannot work and also will not be able to benefits from Canada's health care system.
Have you investigated your immigration options yet? If not, focus on that and dedicate time now to detailed research so that you understand what's possible there.