Can I lose more than I invest in Forex?

You SHOULD NEVER open a Forex Account with any Broker who will not close all Trades if margin falls below minimum margin required to maintain those positions.

All Forex Brokers that I know of and used in past, and will use going forward, will do that Automatically so NO, You can never lose more that you Invest.

As a added feature, my EA is coded to Automatically close all trades when Account Margin falls below a given level it is coded for on that Account.

That fail safe will preserve some equity in Account so No Account will ever go Negative or receive a Margin Call.
Samuel J Sarullo