My view keeps going down

I just entered the new version 1.14.3 and i had this problem. I entered a realm and as soon as i began playing I noticed thet my crossair kept going down. It happened even in singleplayer worlds ( I tought that this was maybe a problem for the realm only but that wasn't the case).

I then entered the game in 1.14.2 and it was fine. I tried to restart my pc and the game but the problem is still there. I can't play in  the realm in 1.14.2 because it's not the last version anymore and this bug annoys me a lot. Also this problem happens only in full screen mode. If i play in window mode it doesn't happen.
Please look after it.

Thanks