The thing is your not being selfish you just relied on that person emotionally so now that your going through a tough time with your mother you have that need for that person who spent so much time on!
There is no right way to grieve for a relationship!
My partners ex took his child from him she had an affair in his house he bought them and then told the court he’d been hitting her for years,
I met him fours months after this.
Long road I assure you!

See it like this, you’ve been close with the same person for four years shared hopes and dreams, talked about creating a new life one day no doubt! You can’t expect a quick recovery it’s impossible! But you do need closure!
Did you ask all the questions you needed to ask? Get everything off your chest?
It’s a work in progress and heartache is ever so painful! You need to remember why you told her to go and you did it for the right reason!
Be strong , get your answers and remember what ur feeling is normal