Hi rajeq,
Your watermelons have flowers but no fruits. There are some factors that causes for not bearing fruits/melons. This maybe caused by the following...
1) Close planting. You need to have a minimum spacing that's essential for all but bush-type melons wich is two by four feet, but most need even more room. Close planting results in little or no fruit production.
2) No pollinators. Watermelons have two flowers; the male and female. To produce fruits there should be some bees, butterflies or even human to pollinate the flowers. See to it that there are bees, butterflies or other insects that would aid in the pollination process.
Don't ever destroy those insects once they're present in your garden.
Happy gardening!
Cris
www.crisramasasa.com