The TV presenter has battled wind and rain in a series of gruelling back-to-back feats of endurance.
She is undertaking the BT Sport Relief Challenge: Davina - Beyond Breaking Point, travelling from Edinburgh to London under her own steam by cycling, running and swimming.
After today's 77-mile (124km) cycle to Windsor, Sport Relief posted a picture of McCall with her head in her hands and the caption: "The moment £davina realised her undercarriage needn't encounter a saddle again for quite some time."
Tomorrow she is due to round off her seven-day journey with a marathon distance run which will bring her to the finish at Tate Modern in London.
The force of the winds she faced between the Peak District and Birmingham was so strong that she had to actually pedal downhill and left her spilling over with anger, she said this morning.
She told BBC Breakfast: "It was awful, misery yesterday, like cycling through treacle.
"I was just going a little bit mad - The Mistral in France sends people 'aaaargh' - I felt like yesterday I was talking to myself, I had to chivvy myself along, I was talking to my sister, saying 'this is what the Mistral is like in France, it's driving me mad'."
During one of her scheduled stops en route, she found herself telling the support team: "I'm really angry, I'm just really angry with the wind."
McCall, 46, said she was in tears as she awoke today but had a visit first thing from comedian friend Mel Giedroyc, who brightened her day.
"I cried this morning, I opened my eyes and started crying and then there was a little knock at the door and Mel walks in - and I was laughing," she said.
McCall has won over the public with her resilience over the past few days with TV viewers seeing her sobbing and barely able to enter the water during a 1.5- mile (2.4km) swim across Windermere on Monday morning. Her body was limp by the time she was dragged from the lake at the other side and she then had to continue her journey in the saddle for the rest of that day.
The TV star has also been battling with the pain of being in the saddle for so long as well as struggling to take in enough nutrition after losing her appetite despite needing to take on board at least 8,000 calories daily to tackle the challenge.
McCall said it was the thought of being reunited with her children which was keeping her going.