Donation concerns/questions, Spain registry

I am currently on the bone marrow/peripheral blood donation registry in Spain--I signed up at my university in the US but since then I have moved to Spain. I got the text that I had a potential match from the US but when I let them know that I live in Spain now they moved me to the Spain registry and now I have a potential match here. I had my blood test today, but before when the doctor was telling me about the procedures (information I already know and have heard multiple times), I got very lightheaded and almost passed out when I stood up. I am not very good hearing about medical things. I used to donate blood but several times I got very lightheaded after and even once had to lay down for about an hour after. I thought it was from the blood donations in the past but since the incident today happened before the blood test I think it is more of a mental response to hearing/thinking about medical procedures. I am not worried at all about the potential bone marrow surgical donation, as I would be under anesthesia. I am worried about a similar response from my body or worse as it would be a much longer procedure than just hearing information about the procedures for 5-10 minutes as I did today. I really do want to donate, but I have a lot of anxiety about a similar situation happening with passing out or vomiting, especially since I live in Spain without family and in another culture/language (I do speak Spanish but obviously it is harder than communicating in English) and I am not sure if my boyfriend would be able to accompany me for the entire procedure due to his schedule. Can you all recommend anything for this situation? The doctor said if neccesary we can do a bone marrow donation instead of the peripheral blood but I know the peripheral blood is more common so I do not want to say I am unwilling to do that type of donation. I am not sure if the doctors here would be willing to presribe and anxiety/other medication since I think it is less common here.