Fat after I give birth

Sherrica • Being a mom is life's best gift!
First kid i was 19 My start weight was 94 lbs i was 174 when I delivered him Never lost all the weight which was good cause i was so small But this Time Age 27 My start weight was 133 dropped to 124 (morning sickness) and now at 5 months im 133 can i go on a diet Pregnant? Im afraid it will be hard to go back to my pre pregnancy weight . I DO NOT WANT TO BE FAT AFTER THIS BABY seems like im getting bigger by the day!! Any Tips ?? 
First baby at 7 months 
2nd baby 5 months