Have you seen bees flying in or around your garden? Must have those "flying pollinators" around to have fruit. If you have had flowers for 2-4 weeks but no signs of melons forming, it may be that bees have not pollinated the female flowers. I have cantaloupes that I have to manually pollinate because there are no signs of bees where I live.
where r u? watermelons can take up to 120+days,need a very long growing season.if you have blooms you should get melons soon