Hi Tom, thank you for writing to us. My name is ***** ***** I'd like to help. I am sorry to hear that your ex-partner has such restrictions on you. It must be hard to feel like you can't have what you want in your own home, especially pertaining to things like treasured memories. And very insensitive and naive of him to comment about your attendance at her funeral. Based on your description, I am making an assumption that leaving and finding a new place to live is not all that easy or preferred, and also that there are some positives here, too, because your ex provides you with companionship when your family does not and you state you like where you live.
The very first thing and among the only things you can do aside from leaving, is to speak openly to your ex about how you are feeling. Express yourself in a calm manner preparing ahead of time what things you are going to say. In all types of relationships, there should be some room for compromise so perhaps having a pet is a hard line that must be respected, but having a set space to display some of your mother's things is flexible. Advocate and speak up for yourself and help your partner understand how you feel, that you pay rent and are entitled to some control over the living space, and what is most important to you and hopefully he will listen and support you.
If you have already tried talking to him and he does not offer any willingness to compromise or be flexible, then you are left with two choices. Accept the situation as is and learn to cope or find an alternative living situation. Sometimes, the acceptance that we cannot control or change other people's behavior, even when we think it is unfair, can be liberating. We can only control our own reactions and should strive to not allow the behavior of others to have great impact when it is outside of our control. Often, this acceptance is easier said than done so engaging in a relationship with a counselor may be helpful in teaching you ways to cope and move on so you don't feel so stuck with the resentment, anger, disappointment and frustration. And of course, leaving is an option in theory too, although as mentioned above, may not be very simple.
So in a nutshell, communicate openly with your roommate about how you feel and your needs. Hopefully he will bend. And if you have done so in the past and he continues to hold strong and not offer you anything, then acknowledge that this is unlikely to change and seek to accept this and find peace. Or, consider how to find a new place to live where you have more freedom.
I hope this helps although I know it must be hard. If you do think talking to someone may help, let me know and i can point you in some directions regarding finding a great counselor.