This might not seem too serious but my boyfriend has been having dreams about his ex girlfriend dying or trying to kill herself. He says they are very vivid dreams that are leaving him depressed for a majority of the day after he wakes up. I've been with him for a little over a year, and known him for almost 3. He was dating this ex girlfriend back when I met him but overtime they broke up. They were constantly on and off actually because either she didn't know what she wanted or she would cheat on him and he would forgive her a few days later. She was always very depressed. She had even tried to kill herself a couple times. Her family grew up very wealthy and her mother has always had issues with depression and suicidal thoughts. I guess this is why he felt he couldn't leave her.
After we met we started hanging out as friends regularly and than things went farther. A couple times while he was dating his girlfriend, me and him had gotten together. I felt horrible but his ex treated him horribly. After a while he realized he didn't want to deal with that anymore and he left her. A few months later me and him officially started dating. She still tried to communicate with him but after awhile she blocked him off everything. Now he's having these dreams of her dying and I'm not sure what they mean. It bothers me but there's nothing I can do.
I basically want to know if this is something I should be concerned about or just something I need to accept or if he still wants to be with her. They had a very serious relationship and I think after how much she hurt him she took a piece of him away.
If anyone can offer me any advice that'd be great. My apologies is this issue doesn't seem like a big deal but its been bothering me and I need some closure.

It should be a big deal for you... these are not normal things most people suffer from. I personally think he has unresolved issues, some related to her, and others that aren't. Both need dealing with or you are going to have a rough ride with him before its over. Granted she had her share of issues......but he has some himself. I think he needs to see a therapist to deal with whatever is causing them.

I've actually had two girlfriends that were killed by drunk drivers WHILE I was still dating them.....so they weren't even an ex at the time....I never had night terrors about it.....though it was painful at the time, and I've never forgotten either, nor have I forgotten most of my previous girlfriends (though I have forgotten some of their names).

I had one wife, killed by a robber and another one die of cancer. Nope, no night mares that left me, where I could not function the next day. Some temp depression, for a short time.

It seems, there is more to his feelings for the ex, since a dream should not be effecting him, since it is just a dream, no matter, how realistic.
And honestly, a ex, that did you wrong, it should be perhaps even bringing some mixed joy.

I will agree, at this level, he needs counseling to find out, the real issues and deal with it

Your boyfriend needs some counseling. He may still be attached to her. You may need to back away so he will get help. Maybe he is not being honest with you or himself.

It could be as simple as healing from his last relationship, which was traumatic, to reliving old feelings he has trouble dealing with. I highly suspect guilt over cheating also, since you DID get together while they WERE together.

Its also a classic rebound scenario, establishing a new relationship, before dealing with the old one first. Unfortunately now he has to deal with all of it and that may take some help from someone other than YOU. He did seem to skip the healing he needed badly, to be a healthy, happy partner, and is full of worry about the consequences of his actions made more intense by her contacting him.

It could take years to resolve all those old intense feelings WITH proper help. Without, on his own, even longer. Just being helpless to help her before, has made him even more helpless now that he has physically left. That's what haunts him the most I suspect. He really does need time and help to get his mind healthy after what he has been through.

'he's having these dreams of her dying and I'm not sure what they mean.'
- Dreams only mean what they mean to the person having them. Only he can know.
'It bothers me but there's nothing I can do.'
- It's good that you say that. He needs to deal with it, and you can support him in varying degrees, or decide that you don't want him this way, your choice.
'.. something I should be concerned about or just something I need to accept or if he still wants to be with her.'
- The concern is how you feel, only. I would guess that he doesn't want to be with her, but that's another thing only he knows. He may be conflicted.
'I think after how much she hurt him she took a piece of him away.'
When you (and he) realize that he is the one who allowed himself to be hurt, you will be much freer of all the baggage. The realization that we don't MAKE people do or feel things, or TAKE pieces away, is an enormous one and difficult to learn. We allow ourselves to get caught in situations that we are free to walk away from, but don't. She had problems before she met him and after she ditched him. He couldn't save her, and wasn't responsible for her happiness.
Therapy will help him understand that. It might only take 2 or 3 sessions, if he gets the right therapist.