A trick that has been suggested before is the following:
You know you can swim two lengths.
Swim two lengths as easily as you can, and when you come to the wall, instead of stopping, turn and push off. When you surface, either take one stroke or stand up, depending on how you feel. You have now broken the two-lap barrier, which is probably more psychological than physical.
From this position you could then try swimming the rest of the length, turning and swimming your usual two lengths. You have now almost swum three lengths.
Another possible approach is to swim your two lengths, turn, roll on your back and swim a length of backstroke or breaststroke, if either of those are in your swimming armoury. Most people find back or breast easier because breathing is easier. I certainly do.