Locked Account

Alright so. This has happened like 5-7 times already and I dont know why. every like 2 days my account gets locked for unknown reasons. It says someone may have accessed my account and done things. Note that all i do is talk to people... I dont post anything really and I only us Facebook messenger. Every time i go through the security check to get my account back it tells em if i want to delete any suspicious activity that has happened around the time and every thing that has happened are things that i have done. talking to people and adding to my story. It asks if I want to delete anything and i say no and go on with my day. that happened like 3 times again later and i had enough and reported the problem then it happens again like a day later. I haven't received anything on the report and it still locks me out. it locked me out today and i cant even get back in now. it wants me to confirm my identity on a different phone or pc that i have used before and i dont know how. i just log in but then it sends me through the regular security thing and tells me to log in on ANOTHER phone or pc again and im confused. This is annoying. i was talking to someone and i cant even log in anymore.