Oh K.... I'm terribly sorry to hear that you're going through this. I miscarried at 14 weeks as well. Unfortunately it wasn't my only miscarriage. I had three more. One at 12 weeks, one at 8 and one at 6. My experience with the 14 week one was this:
Yes, it was painful. Really painful. I would highly recommend that you get some pain medication from your Dr. in anticipation. Particularly if he/she isn't planning to have you in for a D&C. Your doc should have no problem with this.
Sometimes it can take more than 24 hours to fully miscarry. This means that it can come in stages. The bleeding will be pretty heavy but if you find that you're soaking a pad in an hour or less, call your doc. This could mean that you're hemorrhaging.
At this advanced stage it is not uncommon to see fetal tissue. I can't offer you any advice about handling the emotion of this except to say that it can be very intense and something you will likely never forget. Mine was over five years ago and I remember it like it was yesterday. This is something no woman should ever have to experience but that sadly so many do. It's awful and there's no easy way to put that. :(
Some things I've found that helped me: A hot bath (particularly during the most painful time), a heating pad, pain medication, and lots of understanding support.
The pain should subside a great deal after the fetal tissue is passed. So you'll know when things start amping up that it's nearly over. :(
I'm heartsick for you and offer lots of love and support from one woman to another.
Of note: I'm also a doula and work in the labor and delivery dept of a local hospital. If there's anything I can do to help, please don't hesitate to message me.
Hugs - M.