From my own experience of widowhood, I take a different view. I think there are people who for the very best and loving reasons want you to grieve in a certain way. The love you, they worry about you, feel responsible and want you to be "fixed"
but grief is messy....not fixable, certainly not quickly fixable. And, while some help can help, the only person who can get you through it...who can decide what through it even looks like...is you.
So can I suggest that you do yourself a bit of a "how am I" inventory? Right now what do your best and worst days look like? How well are you eating/sleeping/caring for yourself? if you have a pet are you looking after it? You needn't tell anybody the results but its useful to have some idea of how things are with you if you are finding it difficult to be personally objective.
I would have poked myself in the arm with sharp pencils rather than have gone to a grief counsellor, joined a widows choir, had a good cry or been constantly visited and texted. i think if you feel you have had enough counselling then you probab....ly have. I do think that maybe just maybe you need to be a bit more lovingly firm with your son...be doing something when he wants to visit...leave a gap before answering his texts. Make him feel that you are getting on with life in your own way and that he can feel confident to pull back a bit....do a bit of loving realtionship reshaping. If you feel and model being grieving and widowed but still independent MUM then he should feel he doesn't need to be so supportive and (dare I say it) invasive. I think your insight about feeling a burden is significant...not because your son resents you but because you feel your independence and agency slipping away. I hope this helps