The qualifications of a mortal sin:
- It has to be a grave matter.
- You have to know it was a grave matter.
- You have to have done it willingly.
Masturbation (1) is a grave matter and (2) I think, based on your post, that you know it was a grave matter. I can’t comment on (3) and some would argue that if this has been a habit for a long time, you may not have had full willingness or control over your action, which may mean you are not as culpable as someone who knew it was a grave matter and decided to do it anyway because they felt like it.
However, I personally would not feel comfortable receiving Communion with that sin on my conscience.
PLEASE contact a priest and make an appointment for confession, saying you must confess before you are able to receive Communion on Easter. Go to other parishes if necessary (I realize this may be troublesome considering your age but if you could find someone to take you, that would be an option). I doubt a priest would deprive you of absolution if it means you wouldn’t be able to receive the Body and Blood of Christ otherwise.
Prayers for your discernment…I’m sure this is difficult because at 14, you have no choice but to rely on others for transportation, and I pray that you are able to find a solution. God Bless.
ETA: There is this…if you ABSOLUTELY CANNOT get to confession no matter how hard you try - a priest will not see you, you can’t get a ride to confession, etc. - maybe this would apply to you.
The requirement for sacramental confession can be dispensed if four conditions are fulfilled: (1) there must be a grave reason to receive Communion (for example, danger of death), (2) it must be physically or morally impossible to go to confession first, (3) the person must already be in a state of grace through perfect contrition, and (4) he must resolve to go to confession as soon as possible.
(full text can be found here)