Does anyone have any tips on losing weight?

So I went shopping today for some new pants for when I go back to work in January. I am currently on maternity leave with my youngest child. I have 2 kids, a 9 year old and a one year old. Before I got pregnant with my first child back when I was 21 I weighed about 105lbs and was a size zero in pants, after I had him I jumped up to 122lbs and a size 2 then I met my bf and went up to 138lbs and size 4. Now one year after having my daughter I am 160lbs and a size 12! I don’t know how I let this happen, I’m not saying that’s big but that is a huge jump for me, for my height which is 5ft even I am considered obese. When I found out that 12 was my pant size I couldn’t help but feel a little sad. I’ve been really struggling to lose weight lately and it doesn’t help that my bf works in a gym, is super fit, weighs so much less than me, and pokes comments at my weight once in a while.