Ttc advice?

My husband and I are trying for our second baby. We’ve been trying for about 6 months with no luck. Our son is turning 3 next month and we’ve always wanted our kids to be about 3 years apart. Our first was unexpected so we don’t really know much about ttc. I’m about to start doing ovulation tests but I know nothing about them or when a good time is to take them. Since our first didn’t take any trying, we’re getting very hopeless because I haven’t got pregnant yet. Some advice would be greatly appreciated. I’m also a lot heavier than I was with my first, idk if that plays a role or not.