Sources with direct knowledge tell TMZ, Jamie had a massive infection in one of his legs that landed him in a hospital for weeks. He had 5 unsuccessful surgeries to contain the infection, and doctors decided the only way to proceed was amputation.

Jamie is not doing well. He's had other ailments and has been downcast amid the torrent of criticism over his handling of the conservatorship ... something he thinks is terribly unfair. Remember, Jamie is the one who moved from Louisiana to care for his daughter back in 2007. Lots of people who were involved back then say Jamie may have saved Britney's life.

Now here's the interesting twist. Our sources say Britney has softened toward her dad recently. There have been times when she's said she misses her dad, and once even talked about sending him money to help him out.

As for Jamie, our sources say there's nothing he'd rather have than a reconciliation with his daughter, and harbors no ill will.

As we reported, Britney's been trying to mend family fences as of late. She invited her mom Lynne to L.A. over the weekend for her 42nd birthday party, and we're told they got along great. They have been talking on the phone for weeks and are forging a new relationship.

Britney also invited Jamie Lynn to the party, although she was out of town and couldn't attend. BTW, we know Britney is communicating with her sister. Her brother Bryan did join in the fun over the weekend.

Our sources say Britney misses her family and now that she's told her truth in her memoir, she wants to reconnect. Jamie would be the last piece of that puzzle.

What's interesting ... whether reestablishing a relationship with her dad would have an impact on the legal action in play over allegations over the conservatorship.