I've always had spider like veins on my thighs but there seems to be more as of lately. could this be because of weight gain?

Yes, definitely: Spider veins can easily be eliminated by injection therapy at a local vein center in your area.

Look for valves.: Spider veins can be due to many causes including weight gain, trauma, genetics and, most importantly , leaking (refluxing) valves of the saphenous system. If spider veins are increasing you should have a venous evaluation with a venous reflux exam to see if there is an underlying reason for the increased veins. You should see a vein specialist.