Generally speaking, your interest in studying a particular area/particular subject(s) is a main contributing factor to an informed decision regarding whether to take all the subjects that you are contemplating. Given that you love science, this element is satisfied, which indicates that your experience of taking all of Biology, Investigating Science and Physics throughout year 11 and year 12 may end up being a positive one.
Another important factor to consider is your performance potential in each of the 3 science subjects, i.e. how well do you believe you can perform in those subjects if you end up taking all of them? Here, your performance in year 10 Science can be an indicator of your potential in those Stage 6 subjects. Given that your performance in year 10 Science has been favourable, this could be another contributing factor in the event that you decide to take the aforementioned subjects.
As far as I am aware, a possible barrier to taking those subjects is the workload which, as you mentioned, increases as you take more Science subjects. This may in turn increase the chance of the workload associated with each subject becoming overwhelming, which in itself is interesting, especially when considering the fact that you can take Science Extension in year 12 on top of the other Science subjects (which is the maximum allowed, i.e. 7 units worth of Science subjects). However, this may not necessarily be the case given the differing capacities of students. Based on this, the best way to determine whether you can effectively cope with the combined workload of 3 Science subjects is to take all of Biology, Investigating Science and Physics in year 11 and see how you go. If you manage to enjoy and perform well in all three subjects, then you should probably keep them as you commence year 12. Otherwise, you should consider dropping your worst-performing Science subject, consequently reducing the workload, while still allowing you to study subjects that you are interested in. Assuming that compulsory religion is a 2 unit subject, this strategy should work well. If not, you should consider taking an additional subject during year 11.
Of course, it would be great to hear about the experience of BoS users that took 3 Science subjects in year 11 and year 12.
I hope this helps!