Good or bad sign

So my ex-girlfriend broke up with me about 8 months ago. We had been together for about 8 months and were living together for about 7 months. Her reasons for breaking up, she thought we didn’t want the same things in life. I know we want the same things in life, realised after the breakup how unclear I was with what I want and my fellings for her. Guess it’s too late know for letting her know. Shortly after the breakup she went back to her old boyfriend. During the breakup me and my ex were in contact and even went out for dinner a couple of times and had sex. The last time she slept at my place she left in the night, said she had to protect herself. Don’t know if she meant from her feelings for me or just something she said. After a couple of months I started texting her again, but after a couple of texts I got a very angry reply. Here old boyfriend was thinking that we were getting back together and she explained tha she wanted to spend the rest of her life with her old boyfriend. They are now engaged. I didn’t send her a birthday message, asked my brothers girlfriend about sending a text the day after my ex birthday, she told me it was good that I didn’t. She is also one of my x-girlfriend oldest friends and went to her birthday party the following day. Were not in contact with my ex for about 3 months. X-mas is very important for my ex, so I send a text the day after x-mas “Merry X-mas! Hope you are doing well and are having a nice x-mas”. Send it on WhatsApp and noticed that she more or less immediately read the text, no reply which I wasn’t expecting. Don’t know if that is a good or bad sign or doesn’t really matter. The day after I missed a phonecall with no caller ID (have never recieve phonecalls with no caller ID previously), I’m pretty shore she spend her x-mas abroad. Don’t know if it was her or someone else. I know she has moved on and is in a new relationship, but I still miss her alot and which she come back but I won’t interfere in her relationship anymore. I’m trying to move on but it’s hard. Needed to vent and get some opinions.

Ahh, her reading the text quickly means nothing , the substance is that she didn't respond.
The missed phone call.. I wouldn't read into it, she could have left a voice mail, and she will reach out if she needs to.

The protecting herself, in that moment, she probably did have feelings still. But women move on for, breakups differently from men, they're better at coping and recovering (despite what media depicts as the guy always being unphased that's bs)

She's engaged, unfortunately. Nothing you can do but move on, at this point, it's basically over.
I know that hurts.

You should have spoken your truth, at least after she broke things off with you, you should have said something and laid it out, "Look, I do want to keep spending time with you and see where things go, I enjoy the time we spend together, I think you're fun, beautiful, etc. Etc. Let me know if you change your mind"

I don't want to burn you with could have been, should have beens

I prefer to think like this, things couldnt have happened any other way and they happened the way they did.
It was all probably preparing you for something else yet to come.

Got a suggestion that I should be more effective in my communication and give her a call. But I don’t think I will. Firstly, she has made it clear she doesn’t want any more contact since she hasn’t replied to my text. Secondly, don’t want to appear as a stalker crazy ex-boyfriend how don’t want to move on, even though I’m having a hard time doing so. I think she knows what I feel and that I want her back or she might not even think/care about it at all.

Exactly, I was stating you should have said that earlier, meaning basically immediately after she broke things off. Now there would be no point, you need to just let things be and find the next great catch

All I can tell you, my friend, that all the signs are there for you to move on. Your ex is planning and living her life with her current boyfriend. You have to get her out of your system. I understand it's hard, but you have go on and move along, just like she's moving along.

Just always keep yourself available. Some nice woman will eventually come along and catch your interest. In the meantime, stop staring at your cell and pick up a hobby.