Need doctor help! Is taking bisoprolol 2.5mg daily (because of tac) safe when pregnant?

No. It's not recommended in the 2nd or 3rd trimesters and is category c in pregnancy (a is the safest). The only betablocker that is not class c (it's class b) is acebutolol.
Bisoprolol. Bisoprolol has been assigned to category c by fda for pregnancy. It means risk can not be ruled out. Consult your physician for alternatives to discuss.