
it must be really hard to be pregnant and have a fear of needles. I hope you can still make this an enjoyable experience despite it all.
Anyways, why exactly won't they allow you a waterbirth now? It seems quite strange if they won't allow it due to GBS as there have been studies which have actually shown that giving birth in water actually reduced the incidence of babies being exposed and or being ill with GBS in mothers who tested postive. So giving birth in water is actually protective to the baby!
Have you actually considered a homebirth (with a midwife present). Giving birth at home may provide more of the environment you are looking for as opposed to going to the sterile medical environment of a hospital. I'm not sure of the policies where you are but here GBS or being rh negative is not a contraindication to homebirth and you can still have your babies at home if you want to. In fact they can adminster the antibiotics at home as well here and perhaps being at home in your own "safe" environment could help some of the anxiety with the IV insertion???

Just a thought!
Other alternatives include having them insert the IV just long enough for them to run the antibiotics (which generally takes 20 minutes) but then remove it until the next dose is needed. Generally women find the insertion process the most difficult to deal with (which is why it's just inserted once and left in) BUT if you would find it more barable and preferable to have a couple of jabs instead of keeping the canula in then there's absolutely no reason not to do that. With Penicillin (the preferred antibiotic) or Ampicillin it is given every 4 hours. But again there are alternatives which are generally reserved for women with allergies to ampicillin that can be used as well. There's erythromycin (which is administered every 6 hours) and clindamycin (which is administered every 8 hours). With erythromycin and clindamycin there is an increased chance that the type of GBS won't be sensitive or killed by it so it's good to know what medications your GBS is sensitive too before using a medication other then Penicillin.
Also of note, there are many women who do bypass GBS prophylaxis altogether... often for reasons regarding the use of antibiotics themselves..... but not EVERYONE does it... Some women opt to use the risk factor approach in that they will only agree to in labour antibiotics if they develop risk factors that put their babies further at risk of developing eg a fever in labour, prolonged rupture of the membranes, fetal tachycardia (a really high heart rate etc) and other women refuse antibiotics altogether and some even refuse to be screened for it.
There's also numerous natural remedies you can do which can help your body rid itself of GBS including taking acidophilus capsules (the refrigerated kind daily) as well as using garlic (insert a peeled clove into the vagina (sew a string to it so it's not difficult to remove) and keep in inside for an hour or two a day. The acidophilus is a probiotic which encourages the growth of "good" bacteria in the vagina which in turn kills out the bad stuff (like GBS). Yogurt also has probiotics but you would have to eat liters of the plain unsweetened stuff everyday in order to have the same effects as two capsules of acidophilus. And garlic acts as an anti-fungal/anti-bacterial. Another "natural" thing that is protective against baby developing GBS as mentioned above is water birth.
Also of note, just because you have declined GBS prophylaxis for yourself does not mean that you have to agree to your baby getting it. Here, it's recommended that if a woman does not have the antibiotic prophylaxis that the baby is to be monitored for 48 hours for GBS symptoms and only if symptoms present would they start antibiotics. This generally means staying in the hospital (both you and baby for two days... NOT in the nicu btw) though you still have the option of signing yourself out and just bringing baby back if any concerns arise and it's really common sense things to look for eg temperature instability, abnormal breathing, cyanosis (turning blue), abnormal output (all things in my mind a parent is able to assess when known to look for it). Also, here if you have a midwife they will come to your home and do visits at 24 hours postpartum and sometimes on day 2 if needed and on day 3 and 5 and 7 and anytime inbetween if needed....
And in case your interested in the chances of a baby getting GBS it's 1/1000 if the mom DOES not receive GBS prophylaxis and it is reduced to 1/2000 if the mother does receive the antibiotics...... Just to put things in perspective.
Anyways, the point of all my blabbing is that there's not one concrete thing to do and there's different options available to you and only you can decide what's best for you in your situation.
I hope it all works out for you.