Do you always have slippage issue while placing the order?

Slippage is more likely to occur in the forex market when volatility is high, perhaps due to news events, or during times when the currency pair is trading outside peak market hours.

Not at all. It depends and varies from broker to broker. Choose for yourself a broker with decent liquidity providers. There are slight chances of facing this issue with a broker who has high liquidity.

Bit late to the party here - I suggest trying TradeProofer’s EA. It doesn’t trade, but it will measure your slippage, so it’s easy to see if your trade execution is an ‘outlier’ against the general market bid / ask. Tradeproofer have a pretty neat after trade report, which scalpers can also use for entry analysis / profit decay.

In addition to al that is said above, check whether your chart shows bid or ask price. It usually shows sell price, so when you buy the asset with the market order, you get a worse price than what is shown on the streaming chart. If every trade of yours gets the slippage - that might be the case.