Engagement, weightloss, sex?

So I want to get engaged no later than our 7 year anniversary and I told him this already. We've been dating 4.5 years and we are 24. I don't want to get married when I'm 30 or older than that. My goals were to be married by 27-28 years old. I know things change but still. Now comes the weightloss.. I want to be skinnier by the time he proposes which he promised that once I was at my goal weight he'd start looking for rings. (This was all me I told him I didn't want to be fat on my wedding day). And sex.. We have sex it's not uncommon after 4 years for a couple to be intimate. But I feel kinda bad that we did and now there isn't much to look forward to when it comes to marriage.. Like why would he marry me if I'm already doing all the wife stuff without a title