Any website containing payment information will not allow me through

All websites containing payment information will not load or give me access, nor will my xbox one connect whatsoever. I keep being told to authenticate but nothing will go further than that. When my computer blocks off a website it will tell me it is possible my account is under attack. The only website I can access at all is youtube, which makes no sense. Even when resetting my internet and restarting devices I have this problem I have never had before. No one seems to have an answer as to why this is happening but I suspect the account has been hacked. Please help. Otherwise, I will have to drop at&t. So many problems over the years with no real fix. I am truly tired of this.