Why does my car give out when i floor it?

Ok so the car turns on sometimes great but sometimes when i turn it on it struggles on but it does turn on ok then whenever im at a stoplight or stop sign or getting on into an interatate if i floor it the car feels like it goes but then it kind of goes out but the car doesnt turn off so like for an example if im gonna get into an interatate i have to get to 70mph so ill floor it and then it happens and i will have to keep my foot on the gas peddle until it slowly reaches 70mph it also seems like a drinks a little more gas than normal but it runs fine if i just let it go slowly to the mph i need but when i floor it thats when it feels like it goes out.