Ford KA headlights keep blowing

Headlights keep blowing individually and together. Had this car 6 years and its always been keen to blow headlight bulbs 2-3 x a month , although I have never had to replace the other bulbs but now I have
Just replaced drivers side bulb 6 times in 4 days, just waiting for passenger side to go for matching pair.
I have checked all the wiring I can see that goes to the headlight bulb it all seems to be ok , although it very cramped there it hard to see.
The side lights and dipped beam are unaffected its just the headlight bulbs that keep blowing , although on the last three bulbs the glass had started to melt. I have used different bulbs from different car shops, checked the fuse and its ok, any ideas?