If you're questioning whether you are in a toxic relationship or not, here are some clear indicators that suggest that it is a toxic relationship:

Feeling as though they are to blame for the other person's actions
Having to walk around on eggshells to keep the other person happy
Not feeling comfortable expressing how they feel
Avoid all conflict with significant other
Engage in intense conflict often, expressing criticism or negatively about the person
Feel trapped in the relationship
Using a third party to communicate important things
Avoid setting boundaries with the other person
Experience difficulty respecting their own boundaries
Feeling jealousy often, over things the other person has, or if their partner is flirting with another person
Not feeling emotionally supported
Persistent unreliability or predictability

After that, I imagine you'd be asking, can this be "fixed"? I tend to believe that most relationships can be mended if both people agree with the basic premise of respecting themselves and the other person. Working on things together cohesively, and having it be more than one person's effort to change things.

Actionable steps might be:

Sitting and communicating using "I" statements, for example, "I feel angry when I am left out of decision making"
Doing things together that you both enjoy
Telling the other person what you value about them
Stay in the present in conversations so to avoid having a laundry list of things your partner has done "wrong"
Reminding yourself that neither of you are perfect and forgiveness heals not only the relationship but also yourself

You may find that in your relationship you may both communicate that things need to change but it doesn't, or that one person wants it more. At that point increasing your awareness of what you want out of the relationship and life are key. Seeking help sooner rather than later may be of benefit, often when you are in the relationship you are the least objective.