Wanting more, but not wanting to offend

Hey guys so, I've been friends with someone now for a bit and I feel like we've created a good bond between in the short time of being friends. But I've noticed that I have pretty much been putting in the majority of the effort into our friendship and trying to keep it going. This has mad it somewhat debilitating and frustrating because I feel like I shouldn't have to be always putting in the effort. Sometimes I feel like I only exist to them, when they want me to exist and it's taking a toll on my mental health. I wa t to express my frustrations, but they struggle with a plethora of mental illnesses and psychical health problems, that make it hard not to justify those as to why they aren't actively putting in as much energy as me. So in general I feel like if I was to come to them and express my frustrations and ask for more effort, I would be offending them because they know, that I know, they struggle with so much.

what should I do? And how should I tackle this situation? For my mental healths sake and our friendships health as a whole?