New Here

I weigh 159 as if today.. I would love to be 140 by June. Last year at this time I weighed 179. In Aug. I was 151. I recently gained this weigh back so quick, now I cant seem to loose any weight within the past couple months. I just started using this app so I hope it works. I am mom, work full time along with a part time job also, I only make it to the gym about 3 times a week for 45 min. Any tips. Anything at all would be great. I am really frustrated when I look in the mirror. Help
Thanks!