Won't Start...please help...

Hi everyone..can anyone please help me...my 99 cougar won't start..it started acting up a few days ago...won't start ,then it would...seems like when i'd put my headlights on ,the car would start or if i turned them off the car will shut off...??? now it just won't start either way...it will start by crossing at the starter switch.....btw i did have a neon licence lite on & that burnt out...just wondering if that has anything to do with it?? remember it did start doing this slowly til it just won't start at all...thanks to anyone who can offer some help..