Weight gain

I've recently put in a good bit of weight I've been with my boyfriend for 9 months and I a tad self conscious about my belly I used to have a flat stomach as you can see from the first photo i like wearing tight dresses to flaunt my curves but if I put a tight dress on now I look about 4 months pregnant and if it was a baby belly I wouldn't care but it isn't and going on a diet isn't working and I can't afford the gym I'm 17 coming 18 is there anybody who is on a eating restriction or is on a liquid replacement for meals that helped them with their weight quickly???