What in the world am I doing wrong

Everytime I enter a trade either if I'm placing an order or just buying them and there it causes me $450 down INSTANTLY! As Soon as I hit the button. I am new in this, about a week in and I am now trying to paper trade on TradingView but it's frustrating as ever. I can place an order and click "buy" to set the order in place and it'll just enter me when it wants and cause me $500 loss plus more. I'm supposed to be up $10k. I'm down $8k because of this dumb thing. I know I'm doing something wrong cause other traders I watch don't go through this... and plus most of the times my orders don't even place it'll just buy me in at that moment. I was a Buy Start and TP amount but I've seen it move past to and not stop the trade.. or Move past my Blue Buy In line (order) and Not start the trade. This is very frustrating and discouraging and I've been SEARCHING the web on what's happening and it's saying something about slippage. Don't know what it is but I know if I want to buy at a specific spot it should let me with no money loss. Crazy how I enter in and automatically and I mean miliseconds in the trade I'm down $450. Everytime.