I feel like a lot of "How do I know I'm aromantic?" resources focus on never having been in a relationship (god I wish that were me), so here are some signs that you might be aromantic if you are in a relationship and considering it:
• Feels like a performance, or you are copying things you have seen in other relationships
• When people comment on or ask about your relationship, it makes you uncomfortable
• After having sex, the more intimate touches/cuddles do not feel as good
• Wanting more independence or time alone
• Thinking if your partner cheated on you, you wouldn't care
• Being scared that you might cheat despite having no desire to be with anyone else
• Words like "partner, boyfriend, girlfriend, etc" all feel wrong, and you don't like them being applied to you
• Not having a strong feeling of missing your partner like you're "supposed" to
• Questioning your sexuality/preferences despite being confident in who/what you're attracted to
• Feeling like you're lying if you appreciate gifts or affection from them, even if you really do appreciate it
• Saying "I love you" feels fine, but it holds the same weight when you say it to anyone else
• Not wanting to tell anyone about your feelings because you're afraid you will be misunderstood
Anyway, that's all I got. I hope it helps someone out there. I'm still struggling too, but I think we will all be okay! <3