Haven't played this yet but from the sound of it the only way up from here would be a game like summertime saga. Recommend you check it out.
Played both games and I think they are on the same level for me. Their art style is completely different but I think Summertime Saga looks better although it doesn't give back the 3d feeling. I mean I think if Liza had better lips she could've been so much prettier. Summertime Saga has more content and more characters but Sisterly Lust's story is deeper, more serious and more realistic. Like imo in StS pregnancy isn't taken very seriously like ah you got pregnant don't worry, a few weeks and everything will get back to normal. Also it's quite bad that in Summertime Saga Jenny and Debbie can't be called your mom and your sister for some reason idk. But Summertime Saga receives pretty big updates pretty frequently so that's also a good thing. I play Summertime Saga more because it has more content and it has so much potential and will probably just grow bigger and bigger in the next decade while Sisterly Lust is I think just simply perfect as it is.
In Sisterly Lust I experienced so many emotions I totally did not expect it to be this good when I downloaded it and played with it for the first time a few days ago. (Spoilers) When your mom is having that serious talk with the whole family and turns out you've been fucking everyone or when those anti-sex people go to your house and find that you left just hours ago I was so fucking scared they would really bust us. There were moments that were very funny and very sad moments like when you told the youngest sister how you broke up with Sasha, Miley and Sabine. Summertime Saga is funnier and has a lot (I mean A LOT) of pop cultural references some of them are barely noticable but when you do see them it just lightens up my mood.