I (26m) want my girlfriend back 22f)

We have been on/off dating for a year and a half now. We took a break again and I finally realized how much I love her. When I finally told her how I felt, she told me that although she loves me as well, she's confused about how she feels. During our break she met someone else who she only sees as a friend, however, she doesn't know if more will develop between that. She is also worried that I only told her I loved her because it was the "last card in my deck." I took her away for two days to the city and the beach and we had a great time. I also surprised her with flowers today at work. I feel I'm trying my hardest to show her I love her for her, but she just doesn't believe me. I'll admit that I've had my faults throughout our year+ together, but I can't see myself loving anyone else as I much as I love her. What should I do?

TL;DR: She's unsure of me being genuine.