Aubameyang, who joined Arsenal in January, played for former club Borussia Dortmund in the Champions League this season and Uefa's 'cup-tied' rule prevents him from representing his new team in Europe for the rest of the season.
"I am really frustrated because the rules are a bit... I don't know how to say in English but I am disappointed because I can't help my team," Aubameyang told British media.
"When I was in Dortmund, I was playing every three days but now I play once a week or have a long time between games. It is not easy... that's life. I have to deal with it."
Gabon international Aubameyang has scored three Premier League goals in five starts for the club, including in the 3-0 league win over Watford last Sunday.
"I didn't play a lot in January so it was difficult to find the rhythm. Now I'm feeling better. I work hard, I work a lot in the last weeks and I am happy because I feel better," he added.
The 28-year-old will watch from the stands as his team mates take on AC Milan in the second leg of their Europa League last 16 clash at the Emirates Stadium on Thursday. Arsenal beat AC Milan 2-0 in the first leg.
-Reuters