As a submissive leaning switch who has recently started learning how to really dom, I can feel for you.

Don't be afraid to hurt her. You are clearly not a sadist, else that part wouldn't be an issue. The human body is amazingly resilient. As long as you avoid joints, organs, and the face, the odds of doing damage are low. Simply aim for the breasts, ass, and thighs. Start out light, and work up. Practice using your floggers and any other strikers on a pillow so you can be sure of where your hitting every time.

Learn to take control. It is hard, especially if you are not strictly dominant. Depending on how far you are taking it, there are several options. The key is to remind her who is in control. Next time she is feeling amourous, send her to the bedroom with orders to strip, kneel blindfolded, and await your arrival. Wait 5-15 minutes, then go in. If she bitches about waiting, or isn't in the position, punish her. Be clear about why you are punishing her, and make her repeat a saying every stroke of the punishment.

It is hard to do. Being a top is quite different then being a bottom. Don't forget a safe word. Also, if your dick is really too small, use that to your advantage. Tease her about it, how she's never gonna feel a bigger one.