I like to think that when Kal'Reegar said he was out for a week, that just meant he was bedridden for a week. He was probably sick for longer. As for the lovemaking scene between Tali and Shepard, I don't think there was any lovemaking involved. Quarians don't have the same DNA structure as humans, so fluid exchanges would be dangerous. Mordin advises against fluid exchange and whatnot, but offers ways to help ensure both party's safety. He says similar things with fempshep about Garrus, and goes into detail about some of the potential problems. Chaffing. Really, the exchange could be just as dangerous for Shepard as it was for Tali. Her different DNA could result in something toxic. Even just her saliva could make Shepard ill. Based on the other love interest romance scenes, I don't think Tali and Shepard did the deed. Both of the human romance options are in a state of partial undress when the kissing commences. And the aliens are, well, alien but you can see their features already. With Tali, I think it was just a passionate make-out-love-fest. Later when she tells you that it was totally worth it, I don'd think it means that she enjoyed sex. That was probably the first time she'd ever felt any skin aside from her own against hers. Just kissing and cuddling was probably a more intimate experience than sex could ever be. Plus, given the dialogue for Shepard and Tali, I doubt Shepard would be willing to sex it out with Tali even after committing. He wouldn't want to hurt her. Kissing and hugging is dangerous enough.