My son is nearly 22m but is very long for his age. He's still rear facing and not ready to turn it around yet. I'm suddenly finding it awkward to lift him into the seat. Because of his length, I have to "scrunch" him up to fit him through the gap to get him into the seat. He lands awkwardly and I often bump his head on the top of the door frame 
If he was forward facing, I imagine there's more room or he could climb in then up, but I want him RF for a bit longer.
Just to add, he doesn't complain but it also can't be comfortable for him. I'm also 4 months pregnant and have a bad back, and DS is also a little lump so it's all quite difficult.
Has anyone else experienced this? Any suggestions? Guess I'm just looking for some thoughts or is it just me? 