The Felig Chronicles Series by P.J. Dean

Faustina Tina Cain and Nate Lowe each have their own reasons for fighting against a group of aliens, the life-force draining Felig, who have invaded Earth. For Tina, it's personal--they took her mom. Neither Tina or Nate are looking for love--just raw sex to take the edge off possibly vanishing at any moment. Joining forces makes them ponder why they are even alive.

Taken! Tina has been taken by Felig from the home she and Nate shared and had believed Felig-proof. Just when the couple had smoothed out and polished the jagged edges of their relationship. Just when everything had fit together so perfectly. Nate is on a mission now and is learning nowhere is safe and no one untouchable. And most importantly, that allies can be found in the most unexpected of places.