Seperate father have every weekend but she is asking for some weekends

[not a perfect father]

We don't live close like a 2 hour bus journey Ive got a hip problem and I'm autistic and struggle with travel physically and mentally ... So I have every weekend she collected him early on a Sunday so I don't technically have the full weekend and she wants some weekends or every other weekend looking for advice ..... I have to factor in she broke off our 8 year relationship giving me no rhyme or reason so I'm grieving the relationship I don't know why ended and the time Ive lost with my son ..ontop of all my other conditions that have that make all of that a 100 times worse