Got very sick

I got very sick this past week and finally went to the doctor and got some shots.  I could not eat anything and lost about 15 lbs in one week.  I need to know if i should gain my weight back and start losing weight healthy or just start like i am.  I don't feel weak becuase doctor gave me steroids. i am 5' 6'' and weighted 154 lbs and know i am 139 thanks for any advice.

Your weight will return naturally once you can start eating normally again. You'll probably find you feel quite hungry soon and it would be a mistake, I think, to try losing weight straight away.... simply choose nourishing, lighter foods sot hat you get your strength back..  You're not underweight so there's no need to go for deliberate weight-gain.

Wait until you're fully recovered before you actively try losing weight.

Expect much of the weight you lost to return as it will likely be water weight that you lost. To lose 15lbs you would need to have a deficit over the week of 52,500 calories - way more than is possible for one week. It's probably mostly dehydration.

Eat intuitively  - don't try to restrict for the next couple of weeks. If you're hungry, then you should definitely eat. 

And like others have said, you're likely to gain most of that weight back naturally (sorry :/ ). I would guess that you'll probably gain about 10 of the 15lbs. 

Good luck and just focus on getting better!!!! :)