Bottom thread seems too tight!!! Help!!! - Singer 8763 Curvy

If the bottom thread is tight there should also be loops on top and this means that the upper tension is too tight.
Get out your manual (http://www.singerco.com/uploads/download/1198_8763-efs.pdf) and turn to page 24. Under "ADJUSTING TOP THREAD TENSION" it tells you that if you're having thread tension issues, change the tension control dial on the top of your machine from auto. It also shows you a diagram with your problem illustrated on the right side of the page. The bobbin tension is set at the factory, so all tension problems can be solved with top tension adjustment. Set it manually and if it loops on top, loosen the tension a little. Test again. Repeat until loops are gone.
Using different colours on top and bobbin and a contrasting fabric (e.g. black top, white bottom, light blue fabric) means you can easily see what's happening. A perfect stitch is when you see exactly the same stitch pattern on both sides of the fabric. On top, the bobbin thread colour appears between stitches as a tiny dot and on the bottom, you see the top thread dot between stitches.
If it's impossible to get the tension right, take it to a technician, because it's a sign that the hook timing needs attention.