Pairing - whether for programming, carpentry, or any other task - is not about speed. It is about combining strengths. Assuming that the two of you have been paired mindfully and deliberately (which I understand may not be the case) then you have an important role to play in making the pairing work.
For example, perhaps your partner types while thinking and often it all has to be ripped back out. Perhaps your partner roars into the "guts" code that does all the work, but skips the precondition checking and the error handling, only adding them later while debugging. Your style may be closer to what the team wants. The first thing you need to do is to reframe from a deficiency in you: "I am slow" to a strength you bring to the partnership: "I always remember to check the parameters passed in" or "I like to write the tests" or "my code is more elegant".
Then work out a dynamic that harnesses both of your strengths. It's intuitive to let your partner type so you can think, but not if your partner just type a lot that needs to be ripped back out when you finish thinking. It might make more sense to have your hands on the keyboard, and have your partner take notes of the values you see while stepping through, or write scripts to automate the tests you think of. Work together to reduce your partner's frustration and desire to get the mouse and keyboard from you, and your own frustration at seeing someone just run off without thinking. You should end up making each other better.
Or plan B, your bosses are just dumb and you two are a mismatch: pretend to pair but in fact divide the work between you and reconnect every hour or so to share what you've learned and done. But try the first approach first.
