Why is it so hard?!

I got pregnant super easy with my daughter, but she’s 3.5 years old now and I’ve been trying for baby #2 for 3 years now. I was recently diagnosed with PCOS based off my irregular periods and elevated testosterone levels, but I don’t not have cysts. I also don’t seem to have an issue losing weight it’s literally just sticking to eating healthy, but I gave up soda a week ago which has been super hard. I need tips on how to stay motivated. I try to tell myself to do it for my future child, but when sticking to it gets hard it’s to difficult to care. Any advice?? I’m about 180 pounds and I only want to lose 30 pounds.