Hi AstroN. I'm sorry to hear that your kind deeds are backfiring so frequently. I think there are a few things in your chart which are relevant to this.
Others have already mentioned the rising Neptune, with the ruler of the asc and Neptune, Jupiter, also angular and in Pisces. This says much about your empathy with those in need and your willingness to make sacrifices for them. It also suggests a tendency to lose yourself in your interactions with others, being what people need you to be, possibly resulting in confusion, for both yourself and the other, about who you are. It is common for strongly Neptune/Pisces people to attract 'users' who do not really want a proper relationship of whatever kind, but rather want to have their troubles or needs taken care.
The angles on which Neptune and the Pisces Jupiter are placed are the asc and the ic. The house cycle is a cycle of changing viewpoints from which to be self-conscious. Of the four critical points of this cycle - what we call the angles - the asc and the ic are the most subjective, representing types of self-consciousness which we identify with so readily that we don't even know we are doing it. The other angles - the des and the mc - represent types of self-consciousness which we reach for in a more obvious way, providing we can get sufficient leverage against the asc and ic respectively. As well as the des and mc, the Moon, the Sun, Venus and Mars are all ruled by Mercury, and I think that Mercury's exact conjunction with Pluto is very relevant to your situation.
In itself, Virgo needs to feel useful, and also needs to feel that everything is running efficiently. I don't know how this will manifest for you along side the Neptune-Pisces-Jupiter-Sagittarius theme, but these Virgo needs are very important to you on some level. It could be that when you are giving of yourself, you sometimes do so in such a way that others feel like you are trying to control them, even though this won't necessarily be your intention. It could be that you are drawn to those you have Virgo type control issues, making them more sensitive to this.
When we also consider that Mercury is so closely aspecting Pluto, what becomes apparent is that there is a potential for others to experience your help as intrusive - that they may end up feeling disempowered on some level and then react to that. However, I also think it is likely that you are sometimes drawn to people with negative Pluto issues - people who are happy to manipulate you for their own ends, who are more likely to feel disempowered, and who are more likely to turn on you at some point.
The issue of having clearer boundaries has already been mentioned, and boundaries are something that all earthy people need to approach in a healthy and concious manner, especially those who also have something boundary dissolving like Neptune rising and the chart ruler in Pisces. The other things that might be worth considering are, firstly, whether you use helping to get under the skin of others and take control of some area of their lives because this feeds a part of you of which you are not fully aware, and secondly, whether you tend to associate with people who are ruthless and manipulative underneath, even though they seem harmless and nice on the surface.
A couple of other things worth mentioning are Saturn in the 8th sextile the Sun, and Moon trine Uranus (I'm shying away from the wider aspects).
The 8th house represents the type of self-consciousness which arises when we share intimately with others. Saturn shows the area of life where we feel separate and perhaps inadequate, and where we may try to overcompensate and end up feeling a sense of futility and frustration for some reason. Saturn is in a water sign as well as a water house, and its close aspect to the Sun adds to its significance in the chart, and adds to this Virgo Sun's liking of control.
The Moon is in another relationship house - the 7th, which represents the type of self-consciousness which arises when we cooperate with others by following certain principles which are designed to bring about harmony. So your lunar instincts are telling you to interact with others, and this may add to your wish to help people out. But this Moon is in Gemini and is closely aspecting freedom-loving Uranus in the 11th house, which is another relationship house. If you don't recognise your need for breathing space, then others will act it out for you, and if they feel entangled due to your baggage and theirs (as discussed above) then their attempts to reinstate some distance could be messy and clumsy.
These are all speculative thoughts that you may want to consider, but which may not be relevant to you. Feel free to ask for clarification on anything. There is much humility in the way you have opened the thread, and I hope that you are rewarded by something useful in one or more of the replies.
Best wishes,