You are not really getting slipped you are getting exactly what you asked for. A real dynamic market which provides traders with market orders. The market changes in a nano second at times, so because price is not static the price you requested is not always the price which is being offered at that time.
So your not being cheated you are getting precisely what you asked for, the only difference is the price moved prior to your getting filled. In a heavily volatile market the differences can be more glaring then a pip or two and that's even if you get filled. It is possible during times of economic news you may not get filled at all. Bottom line just because you are selling does not mean someone is going to buy what your selling especially during times of uncertainty.
You should if you have not already get a feel for the market during news times where there is a frenzy of activity both from bankers and speculators on news. You will see price moves erratically so if you are planning to participate in this kind of market you should know all bets are off. There are no stops losses nor take profit price guarantees. You are at the mercy of what the market give you during times of heavy volatility. Another consideration are commissions.