Important liquid diet question

I'm about 5-6 days in on the liquid diet and I've noticed that when I drink the protein shakes really slowly I get full off of them and I'm not hungry through out the day. So because of that I have a protein shake for breakfast and one for lunch and sip water all day and then have a broth for dinner. Today I woke up with a bad headache and felt a little nauseous. I haven't even gotten one full shake down, only about half so far and its almost 2pm. I feel very tired as well. I slept in until about 11:15am this morning and I feel that could have contributed to it since I didn't get my morning protein shake.

Any suggestions on what to do? Maybe someone had the same thing happen?

Thank you for your help in advance ????