Dan Wooden and Forest Green loanee Luke Hallett had netted either side of the break to hand Boro a 2-1 advantage heading to the hour mark after they had fallen behind inside a minute.
Yet Chesham rallied and netted three times in the closing stages, through Jaden Thompson-Brissett's double and Jordan Edwards' goal, to secured a 4-2 success.
But Gale was less than impressed at how his side handed the Generals their goals in the defeat. He said: ‘I just feel we've run out of steam. We started the game poorly, as in, they kicked off, Ryan Woodford tried to head it back to the goalkeeper but headed it out for a corner (which they then scored from).
‘To be fair, after that, it was all us. Listen, they threw everything at us - the kitchen sink. They got the equaliser, again a goal we gifted them, we didn't close the lad down and allowed him a free shot.
‘We had five 19-year-olds in the team - did mix it because we're playing on Monday - we are what we are, I just don't want to the season to fizzle out.
‘I couldn't ask the lads to work any harder, they worked their socks off yesterday, but we made some poor choices defensively and gifted them four goals through errors and just not doing our jobs.’
Boro would recover from the setback of falling behind to Shaquille Hippolyte-Patrick's header inside a minute as Wooden levelled things up after 25 minutes. Hallett was then on hand to head home Aston Leigh's corner and complete the turnaround on 58 minutes.
Boro's lead lasted just eight minutes though, as Thompson-Brissett levelled things up again with 24 minutes of normal time left to play.
Thompson-Brissett bagged his second of the game on 84 minutes before Edwards made sure of the victory for the hosts late on.
Gosport, now without a win in four matches, remain ninth in the table with just two games left to play in the league.