Painful tampons post operation

I had an operation in February to remove a myom from my womb and was not allowed to use tampons for 3 months... Now I just got my period today and my doctor cleared me to use tampons again...it's only day one so very light bleeding so I used a mini tampon...putting it in (no applicator) was no problem, had it in for about half an hour when I started feeling it, like it was full already...very uncomfortable...so headed to the toilet to change it...taking it out was a bit painful and it was not full at all... I changed to a pad for now...has anyone experienced this and has any idea what to do??? I really don't like pads, have us d tampons since my second ever period as a teenager...