While it is certainly true that the last few weeks of pregnancy can be uncomfortable, you should not be having severe symptoms like this. I recommend that you get in to see your OB GYN doctor
urgently for an evaluation.
The fact that you are vomiting and having diarrhea
might mean that you've simply caught a common virus or other stomach bug. However, in pregnancy, these can be dangerous because they can lead to dehydration or other problems that might provoke early labor or other complications. Therefore, getting prompt attention and treatment are vital.
The presence of severe lower abdominal pains could also signal a more serious problem. For example, a twisted ovary -- called ovarian torsion -- can occur in pregnancy and is a surgical emergency. Similarly, acute appendicitis
is common in pregnancy women and would also require prompt evaluation and treatment.
Start by getting in to see your doctor as quickly as you can. If you can't get in right away, it would be appropriate to seek help elsewhere, such as through an urgent care center or emergency room, so that this issue does go unaddressed any longer.
I hope that your doctor can figure this out quickly for you!