Best option for first trial of SSRI?

F44, white, 5'4", 63kg, no medication currently, no diagnosis. I believe I am suffering from caregiver burnout leading to moderately severe depression, symptoms include apathy, negative thoughts, intrusive thoughts, inappropriate displays of both temper and sadness, lack of executive function, compassion fatigue, resentment and lately, a certain amount of illogical thinking. My situation in terms of being a caregiver is unalterable. As a result I am seeing my GP to request pharmacological intervention, with the idea that an improvement in mood will hopefully lead to an increased capacity to get things done, which will then break the spiral of failure and guilt and more failure that I feel like I'm stuck in. I've been turned down for talking therapies based on a questionnaire. Here in the UK, the most likely thing I'll be offered to start with is an SSRI. I'm very concerned about two things: first, the potential for feeling worse before I feel better, and second the likelihood of these medications affecting my sex drive. The first concern is logistical: I am a sole caregiver for four adults, three of whom are severely disabled, and two children, one severely disabled and one under the age of ten. Right now everybody is safe and has their basic needs met, albeit not to the standard I'd like. Managing this is my absolute priority, it simply isn't an option for me to have any period of time longer than twenty four hours in which my functioning is lower than it currently is. These people all rely on me and there is no other support available, hence I'm struggling so badly. I've heard that people on SSRIs often experience a dip during the initial period of getting used to the medication, is there any data or anecdotal evidence to suggest which is the one that's *least* likely to cause a dip? And the same question for negative effects on sex drive: this is a priority for me because it's one of the few things in my life that isn't a negative and I would be very unhappy if my libido vanished. I should say, I have already looked at mirtazapine as an option and it won't work for me because of the sleepiness, I need to be able to function on four hours of sleep and can't risk being in a situation where I don't wake at night.