I suddenly had a steady drip from the prssure releif valve so I replaced the valve it the drip went to it opening constantly so I though maybe I had a bad one replaced it again it got worse it would open almost every two hours so I replaced it one more time it didn't leak for two days then it started again but only about twice a day so then I was told to bleed the expansion tank so I did but my prssure releif valve still opens up twice a day what is the problem?

What is your water pressure?

Assuming you are on city water, your pressure reducing valve may be bad. You need to check the house pressure first, it should not exceed 40-50#.