@ rastachito89...good day! actually to ask a second opinion from other vet without terminating first a prior service from the former vet is unethical because you're pitting two professionals. This is true with other professions also. However since your Vet did not even bother to inform you the real cause of the problem and to give advise on what to do while your dog is pregnant, it's actually tantamount of giving up and thus, is telling you that he can't do anything about it (termination by substance). Since there's a termination by substance, you can now ask a second opinion from other vet.
Now with the problem...If It's erlichia, this is my pit bull's medication when she was hit by it. Reminder, she was 6 months old then and obviously not pregnant.
1) Doxycycline caplet (100mg/caplet), 2 caplet, 2x a day for 28 days;
2) Dexamethasone tab (500mg/tab), 1 tab daily for 4 days, 1/2 tab daily for the next 4 days, and 1/2 tab every other day for the next 4 days;
3) Essentiale cap, 1 cap daily for 14 days.