Some good advice above. Being with people who know about your BP and will let you just be yourself in your down times is the best option for not isolating yourself. I hope this older couple can be like this for you. With those kind of people I don't force myself to put up a brave front and just be with them in whatever capacity I can manage. For orgnising the baby shower I would agree with morethingwrong and get help if you can just to take some of the pressure off you.
Best wishes for a good response to the lamactil and the new antidepressant that your doc adds in. Remember it takes time so hang on tight - you will get there.