Losing weight and pregnant?

Okay I’ve always been big, for as long as I can remember ya know. In June of 2018 I was 320, but as of June 2019 I weighed 269. I found out I was pregnant July 1, 2019 and at the end of July I ended up being 280, I was kinda sad because I was walking, eating healthy and stuff but I ended up gaining weight So I have my next appointment 8/22 so I decided to weigh myself yesterday (8/17) and I was shocked because I was back down to 265. I’m kinda confused on what going on with my body. You guys may think “it’s because you started eating better and blah blah blah” but if I’m being honest only in July was I trying to be healthy. I really stopped after July. My baby daddy isn’t trying to be in my life or the child. He doesn’t believe it’s his so I kinda got depressed I guess you can say. I’ve always been struggling with my weight. Before pregnancy I really didn’t care if I ate or not. I would smoke weed and not eat for a day or so and I started seeing the weight dropped but after I found out I’m pregnant I’ve been trying to eat twice a day. I don’t really smoke anymore either and lowkey that’s why I thought I was gaining weight but within 3 weeks I lost 15 pounds. Is this normal? Should I be concerned? Am I just over thinking things? I need some advice and anything would help tbh. Give me your guys opinions please. Thanks in advance tho.