Went A Little Far

Frank is a fake name to stay anonymous. My little sister and I, I’ll call her Ella, have done sexual touching for many years but drew the line at no penetration. I’ve rubbed, licked, and groped but never penetrated and she’s licked and jerked but never entered her. We had always been really careful. I left for college at the end of last year. I got back 2 weeks ago for the summer and we have not gone a night without being intimate. Which leads me to my confession.

Last night, we were grinding as we sometimes did and the excitement made us reckless. Ella was soaked and dripping wet and my dick was covered in the warmth of the fluids. We were quietly moaning but at some point I felt my dick get wrapped in a warm smooth surface. She let out a surprised moan and I realized immediately my most recent thrust went in and my balls slapped against her from how deep I went. We both paused and looked at each other. There was a mix of panic and arousal while we sat there frozen. Finally it was like a mutual agreement was made without saying a word, I was thrusting hard and fast in her. It wasn’t long, maybe 20 seconds and the excitement got to me and I came in her. It wasn’t a lot from how tense the situation felt. Afterwards we talked about it a little and what followed within 30 minutes was the best sex I’ve ever had. Probably 20 minutes at least of sex in so many positions. This time I came like a firehose inside Ella. Everything I didn’t shoot out earlier erupted out of me and then some. Today we went to “get lunch” (plan b) and we’ve barely said anything to each other. Now I’m worried it was a mistake. Ella means the world to me and I don’t want to make things between us bad. Any real advice here?