I've always found agency work more unreliable than indie, having only got one booking in two days from an agency, is not that shocking to me at all. I also find agencies tend to be prone to working on a 'Nandos-esque' business model of pitching to clients what they think is going to be generically popular across the board and less comfortable working with anyone who might vaguely be considered niche. I should say as an aside, though, lots of clients will prefer 'girl next door' to glamorous and size 14 is not really niche either.
The only thing you can do if it you want more clients is to try another agency alongside for a while (use a different name and photos - agencies might say you can't do this but they have no right to make that stipulation) or you could just switch for a while, as long as you leave on good terms agencies usually don't mind women coming and going (well, sometimes they mind but they need you more than you need them - important to always remember! - so they have to suck it up) and/or set up an indie profile if youre able and then see which avenue suits you best in terms of rates and numbers of clients. When you're new, it is often a case of experimenting with the avenues in the industry until you find the method of working that suits you best.