Hey there. You are very young to be on through this, so I hope you have people around you who you can rely on. It will hurt like hell for the first round of anniversaries, birthdays, Christmas, then it gets easier.
Do what feels right for to just now. No, there is no 'right' way to grieve and people understand how you feel, so please don't feel that you are burdening them.
Some people find volunteering helps, but I found it hard, especially when you got some old bugger to visit who would sit there with a fag, moaning about everything and being generally foul to everyone!
The bad memories will fade, but will come back when you're at your lowest, but you will find that you will be able to remember the good times too, and in time, be able to smile.
Remember hat it wasnt your mum in the chapel, just her body. Her soul had already gone. Please don't worry that your mum isn't proud of you - as a mum, she would never want to leave you but when you get the end, you have to go. Sometimes you may feel her presence around (it can take some time though). Yes, the churchman be a comfort and priests are used to being yelled at by the bereaved.
If you need to go to the doctor, do so. Some people need pills (a sister and my brother were on ADs), but please don't drink to blur the pain.
Remember your mum, what she used to say to you, the stories she would tell and remind yourself that you we honoured to have her in your life, even if it was just too short. Think about how she would want you to live your life, and how she would be sad to see you in pieces over her.
It is not fair, it is hard and lonely and sad. Don't forget that there are lots of us on here who have been through the mill, and are on line at all hours of the day and night.