I have been pressing my carotid arteries every day for a year now to check my pulse. sometimes just light but also hard. what's the effects? clots?

Not too hard!: If you compress your carotid too vigorously, you can initiate a reflex that slows your heart and, in the extreme, could even cause you to pass out. (unlikely). If you press hard and long, you can interrupt circulation to that side (hemisphere) of your brain and cause damage. If you must check your carotid, press gently and for no more than 15 seconds.