It's still impossible for us to say- not knowing how well-fed he was when he came into your possession- see? If he was underfed from the start, then yes, eating only once a month for 2 months, then nothing for another month could very well have been starvation. It also depends on what (how much) you actually got him to eat when he did feed for you- there's a big difference between a rat pinkie & a hopper mouse, for example. What exactly did you feed him? I think you said he was small? Mouse pinkies are not even a snack for BPs, & mouse fuzzies are marginal meals- only for really tiny BPs, & even then I'd feed several. Rat pinkies are bigger than mouse pinkies, but still mostly water. Most BPs (of normal size) are actually started on mouse hoppers (weaned mice, eyes open & very active if alive). Mouse hoppers are about half the size of adult mice.
I know how bad it feels to lose a pet...that's something most of us have experienced, & sometimes it is a result of, or compounded by, our unintentional mistakes. Don't beat yourself up, just learn from any mistakes made.